#internals-and-peps | Python | Page 52

strange fog Jun 27, 2020, 8:25 AM

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locks, semaphores, the works

hazy anchor Jun 27, 2020, 8:26 AM

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I'm not sure I see a huge benefit

red solar Jun 27, 2020, 8:26 AM

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to using atomics?

hazy anchor Jun 27, 2020, 8:26 AM

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But I personally haven't using much shared memory in python

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I'm familiar with them and the use in other languages, but it's never a tool I've wanted and not had in python. Guess I write different programs in it

strange fog Jun 27, 2020, 8:27 AM

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on windows you'd be using one of these for example http://timgolden.me.uk/pywin32-docs/win32event__CreateMutex_meth.html

on linux/osx you'd be using SYSV/POSIX primitives

red solar Jun 27, 2020, 8:28 AM

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the one benefit of atomics is that they don't (usually) block

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which is ideal within an event loop

strange fog Jun 27, 2020, 8:28 AM

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this problem keeps evolving

red solar Jun 27, 2020, 8:29 AM

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there isn't really a defined problem, i want atomics in general 🤷

strange fog Jun 27, 2020, 8:29 AM

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so it's atomics for IPC inside an event loop?

red solar Jun 27, 2020, 8:29 AM

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that's a use case yes

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another is if i want a process safe variable in shared memory, if i put a lock there, how would c++ access said lock?

strange fog Jun 27, 2020, 8:30 AM

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you use one of the synchronization primitives provided by the kernel

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which have their own way of being ID'd system wide

red solar Jun 27, 2020, 8:31 AM

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from python? how?

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(i got this added in python 3.10 sorta but before that?)

strange fog Jun 27, 2020, 8:31 AM

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well for windows you can use pywin32 to access the windows api

red solar Jun 27, 2020, 8:31 AM

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through ctypes?

strange fog Jun 27, 2020, 8:31 AM

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and for linux/osx im sure there's a SYSV or POSIX api somewhere

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pywin32 is a module that exposes the windows api to python

red solar Jun 27, 2020, 8:32 AM

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ah huh

strange fog Jun 27, 2020, 8:32 AM

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i linked one of the doc pages above

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for creating a mutex

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http://semanchuk.com/philip/posix_ipc/

red solar Jun 27, 2020, 8:33 AM

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hmm... ok i guess the uses cases are for shared memory if you don't want the overhead of locks, and for process safe non blocking locks (complicated but doable)

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(non blocking as in for use with asyncio)

strange fog Jun 27, 2020, 8:34 AM

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to have interprocess atomics like youre suggesting im pretty sure you'd need some backing from the kernel

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and idk of any kernel that provides this

hazy anchor Jun 27, 2020, 8:34 AM

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It seems like a use case almost entirely done at the cpython level

red solar Jun 27, 2020, 8:34 AM

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all lock free atomics are interprocess safe

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the second one yes, the first one no

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and if they're going to be used for the second one, why not provide that freedom to everyone 🤷

strange fog Jun 27, 2020, 8:35 AM

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are you sure youre not thinking of thread safety?

red solar Jun 27, 2020, 8:35 AM

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yes

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https://stackoverflow.com/questions/51463312/are-lock-free-atomics-address-free-in-practice

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(c basically stole their atomics from c++)

hazy anchor Jun 27, 2020, 8:36 AM

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Describe a program that you would use this hypothetical library in

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I'm not against it, I just want to understand

red solar Jun 27, 2020, 8:37 AM

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beyond the event loop thing?

hazy anchor Jun 27, 2020, 8:40 AM

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Atomic operations are pretty limited. Simple maths and pointer swapping. What would you be doing in asyncio that was best solved by having two corouines accessing the same variable

red solar Jun 27, 2020, 8:42 AM

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so people in asyncio rn can't use thread/process locks

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they block

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there are OS primitives that let you have non blocking locks, and they almost always have a file descriptor (int) as a handle

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so now you can use this handle with poll/select/epoll whatever, to implement an asyncio friendly lock 🙂

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great for mixing threads, and event loops, since in python int is already thread safe

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but it's not interprocess safe

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and you cant put the file descriptor in shared memory and have it be safe as is

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so make it an atomic int 🙂

hazy anchor Jun 27, 2020, 8:47 AM

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It sounds to me like a coroutines aware lock primitive is what's required there. Maybe it can be achieved with atomic support, implemented in C using the atomics that already exist

red solar Jun 27, 2020, 8:48 AM

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this is what i'm working towards (other people helping), just realised i might need atomics for this, and thought why not propose it as part of the library, so other people can use it for their really niche use cases?

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imo the more available directly rather than as an implementation detail, the better

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also x86_64 has 128bit atomics which is nice 🙂 (fits a uuid)

hazy anchor Jun 27, 2020, 8:49 AM

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But to do what

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You can't do fuck all operations on a uuid

red solar Jun 27, 2020, 8:50 AM

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maybe you want to make some sort of in memory interprocess database 🤷 idk people do crazy things (definitely not me)

hazy anchor Jun 27, 2020, 8:52 AM

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Well. I'm interested but not convinced. Lucky you don't have to convince me :p if it's going on GitHub would you care to drop a link

red solar Jun 27, 2020, 8:53 AM

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i'm currently rethinking the implementation 😂 writing an atomics library based on <stdatomic.h> is easy, but if you want 128bit atomics and stuff, you need intrinsics :/

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i can link you to a partially complete old implementation?

strange fog Jun 27, 2020, 8:53 AM

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intersting SO post. one question

The mechanism hardware exposes for atomic read-modify-write operations is based on MESI cache coherency which only cares about physical addresses. x86 lock cmpxchg / lock add / etc. makes a core hang on to a cache line in Modified state so no other core can read/write it in the middle of the atomic operation.

what happens if it's a single core running multiple processes accessing the same address

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does that violate the atomicity?

red solar Jun 27, 2020, 8:55 AM

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no, but i'm trying to think why

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on x86 specifically that's not an issue, since all int operations are atomic (but not in the sense that the cache will be updated for other cores)

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but if there's no other cores to update, then it's just always atomic 🤷

hazy anchor Jun 27, 2020, 8:58 AM

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Do I interpret the above uses a memory guard in the cache? That seems like a non starter doesn't it

strange fog Jun 27, 2020, 8:58 AM

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thats what im understanding

red solar Jun 27, 2020, 8:58 AM

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why is it a non starter?

hazy anchor Jun 27, 2020, 8:59 AM

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But it seems like in C++ the operation is explicitly supported

red solar Jun 27, 2020, 9:01 AM

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yes it does use a lock in the simplest sense (hence the lock prefix on the instruction), however it's a hardware lock at the lowest level, and it's process safe (it applies to all cores on a machine)

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(all cores that share that cache)

hazy anchor Jun 27, 2020, 9:02 AM

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I think I'm more likely misunderstanding the cache line part. Research suggests it can work

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I wonder if multiple cpu machines are the edge case

red solar Jun 27, 2020, 9:03 AM

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to be clear, this can still block, just realistically almost never, and if it does, it's for a tiny amount of time)

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edge case in what? cache coherency is a multi core thing

hazy anchor Jun 27, 2020, 9:04 AM

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It must be a solved problem for atomics to work at all, so disregard me. It's interesting and not something I know about

lucid coyote Jun 27, 2020, 12:01 PM

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Is there a way to use functools lru cache for large memory requirements (e.g, graph isomorphism checking and path detection) without crashing your computer?

radiant fulcrum Jun 27, 2020, 12:02 PM

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more ram

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™️

hazy anchor Jun 27, 2020, 12:02 PM

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Swap, specifically

lucid coyote Jun 27, 2020, 12:02 PM

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Could you give an example?

hazy anchor Jun 27, 2020, 12:02 PM

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Swap as in swap space, it's disk backed memory

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Allocate more of it

lucid coyote Jun 27, 2020, 12:03 PM

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Oh, ok

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Thank you very much!

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Sorry about that

hazy anchor Jun 27, 2020, 12:04 PM

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See how ya go. It's generally not that fast, but a cache for objects larger than memory than only be optimised so much. The critical point is probably to keep the keys in memory and swap out the value

lucid coyote Jun 27, 2020, 12:14 PM

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That helps a lot, thanks!

austere spruce Jun 27, 2020, 1:39 PM

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How do you guys specify your version of installable packages that you create? I want to define it one place and then being able to get the version from within my code (to set FastAPI version)?

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I ended up doing the following:

.
├── alembic.ini
├── docker
│   ├── Dockerfile
│   └── Dockerfile.worker
├── docs
├── Makefile
├── MANIFEST.in
├── migrations
│   ├── env.py
│   ├── helper
│   │   └── __init__.py
│   ├── README
│   ├── script.py.mako
│   └── versions
│       ├── 2d1946f92088_added_users_table.py
│       └── added_users
├── README.md
├── setup.cfg
├── setup.py
├── src
│   └── wert_api
│       ├── asgi.py
│       ├── config.py
│       ├── __init__.py
│       ├── models
│       ├── routes
│       └── version.py
└── tests
    ├── conftest.py
    └── test_users.py

Where version.py simply contained __version__ = '0.1.0'
And setup.py:

# -*- coding: utf-8 -*-
"""Builds boilerplate as a package

"""
import setuptools
from distutils import util

version = dict()
path = util.convert_path("src/wert_api/version.py")
with open(path) as file:
    exec(file.read(), version)

setuptools.setup(version=version["__version__"])

unkempt rock Jun 27, 2020, 2:20 PM

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why not import version from version?

minor sinew Jun 27, 2020, 2:36 PM

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how can i test if 2 types are equal?

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for example, if i take a type as a function input, how do i equate that input type with some other type?

open trout Jun 27, 2020, 2:38 PM

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if type(obj1) is type(obj2):

lunar trail Jun 27, 2020, 2:38 PM

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You're asking in the wrong place btw @minor sinew. Use the help channels for help (see #❓｜how-to-get-help)

minor sinew Jun 27, 2020, 2:38 PM

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@open trout that's not what im asking. in that, you're getting the type from some object

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the type im getting is a function input, so there's no object to even compare

lunar trail Jun 27, 2020, 2:39 PM

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@minor sinew As I said, move to a help channel please

boreal umbra Jun 27, 2020, 4:32 PM

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I feel like there should be a flatten function in the stdlib for flattening 2d lists

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it's such a common problem with no universal solution.

unkempt rock Jun 27, 2020, 4:38 PM

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values = [[1, 2, 3], [4, 5], [6]]
flattened = [e for row in values for e in row]

Though I agree. a flatten() function that flattens any list or maybe a flatten(axis) would be really conventient

flat gazelle Jun 27, 2020, 4:38 PM

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for lists you can do sum(values, []), but we could absolutely use a flatten function

unkempt rock Jun 27, 2020, 4:39 PM

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wow that's actually quite clever. Never thought about that

austere spruce Jun 27, 2020, 5:43 PM

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@unkempt rock that would make it uninstallable for new users since src is not a module.

minor sinew Jun 27, 2020, 5:48 PM

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finally finished testing this function i made to build a big matrix to represent connections in a big network lol the worst part was handwriting the expected test case matrices

tawdry pine Jun 27, 2020, 5:50 PM

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Looking for advice in implementing Domain Driven Design, Event sourcing using python.

pure sinew Jun 27, 2020, 6:52 PM

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Does anyone here have experience dealing with neural networks in python?

flat gazelle Jun 27, 2020, 6:52 PM

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#data-science-and-ml

pure sinew Jun 27, 2020, 7:23 PM

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Thanks

rugged lantern Jun 27, 2020, 8:46 PM

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With cpython wouldn't each element in a list be different sizes as they don't have to be the same type?

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(Same size in memory)

charred wagon Jun 27, 2020, 8:47 PM

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Doesn't it just store pointers to objects?

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And pointers are always the same size

void sonnet Jun 27, 2020, 8:49 PM

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i was thinking that they're pointers, but i haven't looked so its just a guess/assumption from me.

rugged lantern Jun 27, 2020, 8:49 PM

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So it's not an actual c array then?

grave jolt Jun 27, 2020, 8:49 PM

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It is an array of pointers.

void sonnet Jun 27, 2020, 8:49 PM

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an array of point... yesh. thats. 😄

charred wagon Jun 27, 2020, 8:50 PM

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https://docs.python.org/3/faq/design.html#how-are-lists-implemented-in-cpython

rugged lantern Jun 27, 2020, 8:50 PM

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Ok cheers

grave jolt Jun 27, 2020, 8:50 PM

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But different objects on their own, of course, can occupy different amount of space.

rugged lantern Jun 27, 2020, 8:50 PM

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Yea that makes sense

charred wagon Jun 27, 2020, 8:51 PM

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They're just somewhere in the heap aren't they

rugged lantern Jun 27, 2020, 8:53 PM

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👍

grave jolt Jun 27, 2020, 8:58 PM

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Well, all objects are in the heap, yes

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in CPython

swift imp Jun 27, 2020, 10:30 PM

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I got a question about compiling an exe and making a gui in python. I wrote a function that takes in an excel sheet and for each row in the sheet, it uses selenium to fill out an online webform. Now I want to distribute this among the company I work for, so others can use it. If u compile this into an exe, how do I package it so the chrome driver.exe that's necessary for selenium to control chrome, is inside that .exe

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I know nothing about doing this in python so like, idk if what I want us possible

somber halo Jun 27, 2020, 10:30 PM

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you can try PyInstaller

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https://pyinstaller.readthedocs.io/en/stable/operating-mode.html#bundling-to-one-file

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wait, just read about the need of adding chrome driver.exe too

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I think you could try to build it as a folder and wrangle the building step in PyInstaller in order to ship that .exe

swift imp Jun 27, 2020, 10:43 PM

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Ok, thank you

split chasm Jun 27, 2020, 10:47 PM

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Yeah you can do it with pyinstaller, but it has a lot of "gotyas". Might take some time to understand hidden imports and data packages for it

golden summit Jun 28, 2020, 1:51 AM

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hey is anyone here familiar with ~~multithreading~~ multiprocessing* and database connections ?

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i am trying to use multiple cores to make simulatenous inserts into a db and im getting a crash thats very odd

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def createRandomOLD(mean, standardDeviation, numberOfUniques, SensorType,sensorID):
   
    for k in range(numberOfUniques):
        randomG = ('%.2f'%(random.gauss(mean,standardDeviation)))
        print("Creating Entry with value " + randomG + SensorType)
       
        cursor = dataBaseConnection.cursor()
        cursor.execute(
            'insert into SensorData(SensorUniqueID,SensorValue,SensorInput,SensorType,IsMalware) values(?,?,?,?,?);',
            (sensorID, float(randomG), 'Virtual',SensorType,0)
        )
        dataBaseConnection.commit()

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so im making two threads that call this function with different input parameters.
The error that i get seems to be an issue with syncronization?

spiral willow Jun 28, 2020, 1:54 AM

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What database?

golden summit Jun 28, 2020, 1:54 AM

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its MS SQL Server

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and the device thats running this is a raspberry pi 4

spiral willow Jun 28, 2020, 1:55 AM

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What’s the error?

golden summit Jun 28, 2020, 1:55 AM

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let me get it for u!

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is it ok if i get a screenshot?

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im like remoted into

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📎 unknown.png

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📎 unknown.png

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📎 unknown.png

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and sometimes i get that error with no changes to the code

spiral willow Jun 28, 2020, 2:00 AM

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maybe multiple unique keys trying to be written

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malloc screams memory

golden summit Jun 28, 2020, 2:01 AM

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worth mentioning that if i run this on my desktop i get no errors

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and i tested it with 16 processes and it worked fine

spiral willow Jun 28, 2020, 2:01 AM

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ok

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I think it might be Python error and not an MSSQL error

golden summit Jun 28, 2020, 2:02 AM

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yeah its odd

spiral willow Jun 28, 2020, 2:02 AM

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where is MSSQL server running?

golden summit Jun 28, 2020, 2:02 AM

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this also freezes up the sql server

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its running on a dedicated server at a university

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so they are hosting it with what i assume to be good hardware and all that

spiral willow Jun 28, 2020, 2:02 AM

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you have to restart MSSQL?

golden summit Jun 28, 2020, 2:02 AM

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i dont

spiral willow Jun 28, 2020, 2:02 AM

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they do?

golden summit Jun 28, 2020, 2:03 AM

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what frees up the db

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is killing my vpn connection to the university***

spiral willow Jun 28, 2020, 2:03 AM

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are you properly committing?

golden summit Jun 28, 2020, 2:03 AM

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i beleive using try: and finally: has stopped that error

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So im not too sure if i am

spiral willow Jun 28, 2020, 2:03 AM

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you could read back

golden summit Jun 28, 2020, 2:04 AM

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im committing every time a value is generated by the funciton

spiral willow Jun 28, 2020, 2:04 AM

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with it being RaspPi, I wonder if it can't handle the load

golden summit Jun 28, 2020, 2:04 AM

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idk if thats helpful

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hmmmm

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yeah im wondering

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its a 4 core model with 4gb of ram so i expected it to

spiral willow Jun 28, 2020, 2:04 AM

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and malloc error is memory allocation errors

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but it's not freeing up memory properly

golden summit Jun 28, 2020, 2:05 AM

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yeah the hated word from my c/c++ experiences

spiral willow Jun 28, 2020, 2:05 AM

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I'm not familiar with multithreaded library either

golden summit Jun 28, 2020, 2:05 AM

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thats fine

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if this were your program to troubleshoot what steps would u take?

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single threads work fine* idk if i mentioned that

spiral willow Jun 28, 2020, 2:05 AM

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I can tell you that MSSQL can handle numerous applications dumping garbage in it

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we use it at work all the time

golden summit Jun 28, 2020, 2:06 AM

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yeah the server is set to unlimited connnections

spiral willow Jun 28, 2020, 2:06 AM

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instead of multithreaded library

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run it with just two SSH windows and python app (no multithread)

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maybe third SSH windows to watch top to make sure you don't swap and explode

golden summit Jun 28, 2020, 2:07 AM

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yeah so thats where we run into an issue

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we have been told that it should all run from one script

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and on a rpi

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but that does work

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we have tried that with like 4 seperate terminals

spiral willow Jun 28, 2020, 2:08 AM

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so make a script that runs 4 python3 app.py?

golden summit Jun 28, 2020, 2:08 AM

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so 1 script that launches all the others?

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i think we tried that and it finishes the scripts in order and not simulataneosly

spiral willow Jun 28, 2020, 2:09 AM

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I'm not familiar with Python launching stuff

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I use Powershell for my OS level work

golden summit Jun 28, 2020, 2:10 AM

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ah ok

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thats fine i appreciate the help

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i think we may have to do that and move on

spiral willow Jun 28, 2020, 2:10 AM

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I wonder if Multiprocessing thread is keeping track or something and in middle of keeping track, runs out of memory and crashes

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are you spawning or forking?

golden summit Jun 28, 2020, 2:12 AM

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hmm im not sure what spawning and forking is

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i believe im spawning if youre referencing the creation of the thread

spiral willow Jun 28, 2020, 2:13 AM

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ok

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yea, I mean multithreading this may or may not speed things up

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probably will because SQL IO is long

golden summit Jun 28, 2020, 2:14 AM

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our intention is to be able to change the rate of inserts per thread,

for example thread 1 inserts every 5 seconds while thread 2 inserts every second

spiral willow Jun 28, 2020, 2:14 AM

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you could see if pyobdc supports async

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:butwhy:

golden summit Jun 28, 2020, 2:15 AM

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we are emulating sensors with varying poll rates

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but im starting to think more and more just use seperate scripts and say its easier this way

spiral willow Jun 28, 2020, 2:16 AM

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you should make time between inserts an argument for the script

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python3 insertdata.py 5

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https://www.tutorialspoint.com/python/python_command_line_arguments.htm

Python - Command Line Arguments - Tutorialspoint

Python - Command Line Arguments - Python provides a getopt module that helps you parse command-line options and arguments.

golden summit Jun 28, 2020, 2:17 AM

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thanks for the help!

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ill look into it

spiral willow Jun 28, 2020, 2:18 AM

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so you have a script that is python3 insertdata.py 5;python3 insertdata.py 2;so on

golden summit Jun 28, 2020, 2:18 AM

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i see

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thats useful

gleaming rover Jun 28, 2020, 7:07 AM

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in general, I think argparse is preferred to getopt

mystic cargo Jun 28, 2020, 3:36 PM

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If I'm not wrong, getopt is depreciated in favour of argparse

boreal umbra Jun 28, 2020, 5:38 PM

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Isn't None fundamentally just a sentinel with a falsey bool value?

unkempt rock Jun 28, 2020, 5:43 PM

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#help-coconut

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can anyone takea look

peak spoke Jun 28, 2020, 5:49 PM

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Should be pretty much just a singleton with the false bool value and some additional small things like the repr @boreal umbra here's the relatively short implementation https://github.com/python/cpython/blob/master/Objects/object.c#L1511-L1632

boreal mantle Jun 28, 2020, 7:07 PM

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anybody use any of the libraries here for data validation or derivatives of them for dictionaries from external sources (for example, fetched from an http request, etc)
https://github.com/mahmoudimus/awesome-validation-python

GitHub

mahmoudimus/awesome-validation-python

Python Validator Libraries. Contribute to mahmoudimus/awesome-validation-python development by creating an account on GitHub.

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kind of just looking for a simple validation library that i can write my own custom rules for and isn't too complicated but would be a lot of libs to test out by hand lol

hollow crane Jun 28, 2020, 7:34 PM

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rip advanced-python

oblique crystal Jun 28, 2020, 8:01 PM

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it's only a name change

paper echo Jun 28, 2020, 8:22 PM

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@boreal mantle i use marshmallow and jsonschema for this

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I actually really would love a library that automatically generates a marshmallow schema from a jsonschema

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Or vice versa although that will entail some restrictions on the marshmallow schema

hybrid shell Jun 28, 2020, 8:34 PM

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Wait wait..

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#advanced

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ah..

narrow kettle Jun 28, 2020, 8:37 PM

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does python have a built in code generator? i need to generator some repeated code

flat gazelle Jun 28, 2020, 8:38 PM

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no, there are no convenient macros. Your best bet is making it in a loop or possibly eval

narrow kettle Jun 28, 2020, 8:39 PM

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hmm, when you say eval, can i generate code that can then be used in the project it self

pliant tusk Jun 28, 2020, 8:39 PM

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@narrow kettle would it not work simply as a function?

narrow kettle Jun 28, 2020, 8:40 PM

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well its generating functions

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if thats what your asking

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in C# id use a source generator

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https://devblogs.microsoft.com/dotnet/introducing-c-source-generators/

.NET Blog

Phillip Carter

Introducing C# Source Generators | .NET Blog

We’re pleased to introduce the first preview of Source Generators, a new C# compiler feature that lets C# developers inspect user code and generate new C# source files that can be added to a compilation. This is done via a new kind of component that we’re calling a Source Gene...

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to get an idea what i want

pliant tusk Jun 28, 2020, 8:41 PM

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can i see what your use case is?

flat gazelle Jun 28, 2020, 8:41 PM

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what is the actual goal here. It should be possible by setting module attributes or similar depending on what you are doing

narrow kettle Jun 28, 2020, 8:41 PM

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i had an idea to generate decorators for all the events in my messaging system

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ive been working on this for some time, with several different ideas but none have panned out

flat gazelle Jun 28, 2020, 8:42 PM

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so you have a bunch of event classes and want decorators for them?

narrow kettle Jun 28, 2020, 8:42 PM

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i have a bunch of events

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the events are just strings

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i need to generate decorators for each one

pliant tusk Jun 28, 2020, 8:42 PM

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you can make a function inside a function

narrow kettle Jun 28, 2020, 8:42 PM

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yee thats how decorators work

pliant tusk Jun 28, 2020, 8:43 PM

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like ```py
def x(num):
for i in range(num):
def f():return i
yield f

narrow kettle Jun 28, 2020, 8:43 PM

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and how does this help me?

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i need to generator decorators lol

pliant tusk Jun 28, 2020, 8:44 PM

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so you could gen all your decorators like that?

narrow kettle Jun 28, 2020, 8:44 PM

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can i then use them in the project

flat gazelle Jun 28, 2020, 8:44 PM

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for event_string in events:
    def decorator(): ...
    globals()[f'on_{event_string}'] = decorator
``` do be careful that you cannot use event_string inside the decorator function

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would be the shitty metaprogrammy way

pliant tusk Jun 28, 2020, 8:45 PM

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or you could create a dict then add that dict into your modules scope, or put them as properties on a class

narrow kettle Jun 28, 2020, 8:45 PM

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i want the freedom to have the event name and the function name differ

flat gazelle Jun 28, 2020, 8:45 PM

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ye, this would be better as class attributes.

narrow kettle Jun 28, 2020, 8:45 PM

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uhh

#

elaborate on that?

#

wdym class attributes

charred wagon Jun 28, 2020, 8:46 PM

#

You can assign new attributes to objects after they've been defined and even instantiated.

narrow kettle Jun 28, 2020, 8:46 PM

#

ya thats what ive been working on

paper echo Jun 28, 2020, 8:46 PM

#

Python can generate source from AST no?

pliant tusk Jun 28, 2020, 8:46 PM

#

class events:
  ...

setattr(events, "on_event_2", func)```

narrow kettle Jun 28, 2020, 8:46 PM

#

i need to apply the decorator at instance creation

paper echo Jun 28, 2020, 8:47 PM

#

Cant do that J

#

It's a common request

narrow kettle Jun 28, 2020, 8:47 PM

#

you can

paper echo Jun 28, 2020, 8:47 PM

#

Not possible with the way classes are defined

narrow kettle Jun 28, 2020, 8:47 PM

#

i did it yesterday, the problem was it doesnt work with decorator args

paper echo Jun 28, 2020, 8:47 PM

#

You have to do it in init

#

Not with a decorator

narrow kettle Jun 28, 2020, 8:47 PM

#

one sec ill show you

pliant tusk Jun 28, 2020, 8:47 PM

#

i mean you can hook class creation

charred wagon Jun 28, 2020, 8:47 PM

#

Can't you do it with __new__ or something?

pliant tusk Jun 28, 2020, 8:47 PM

#

technically

final whale Jun 28, 2020, 8:47 PM

#

hmm

flat gazelle Jun 28, 2020, 8:47 PM

#

oh, do you have the

class A:
    @self.dec
    def fun(self):
        ...
```problem

paper echo Jun 28, 2020, 8:47 PM

#

Yes exactly

narrow kettle Jun 28, 2020, 8:47 PM

#

no you have to override __get__

#

in the decorator class

paper echo Jun 28, 2020, 8:48 PM

#

The point is it's not built into the language and you have to use your own introspection logic to get it to work

flat gazelle Jun 28, 2020, 8:48 PM

#

ye, there are a few ways to get around that

paper echo Jun 28, 2020, 8:48 PM

#

There are several ways to implement it

#

But none of them are built into the language

#

Personally I think overriding attribute access is the wrong way to go about it

#

You should do what the attrs lib does imo

#

"Mark" a method with a decorator

final whale Jun 28, 2020, 8:48 PM

#

that sounds like the thing that dpy uses for cog listeners, maybe you can take a look at it

paper echo Jun 28, 2020, 8:49 PM

#

Then in __new__ replace the marked methods with the decorated version

#

@final whale that too

narrow kettle Jun 28, 2020, 8:52 PM

#

one sec let me sort back through my git history to find what im talking about lol

#

from functools import partial
class Decorator(object):
    def __init__(self, func):
      self.func = func

    def __call__(self, *args, **kwargs):
      print(f'__call__ {args}')
      return self.func(*args, **kwargs)   

    def __get__(self, instance, owner):
      print(f'__get__ {self}')
      return partial(self.__call__, instance)

class ham:

  @Decorator
  def eggs(self):
    print('hello from eggs')

#

this allows you to get the instance ref

#

which you can then use to assign the decorated method reference

#

originally i wanted to have it so i could do @Set('the_event_name')

#

but for the life of me i cant figure out how to get the acutal method reference and not just the object instance

#

but if i can generate those for every event then i can just have a non parameterized decorator for each event

#

@messenger.some_event

#

instead of @Messenger.Set('some_event')

#

whoop

pliant tusk Jun 28, 2020, 9:03 PM

#

@narrow kettle just make Set return Decortator

narrow kettle Jun 28, 2020, 9:03 PM

#

i tried all manner of versions of that

#

could not get it to work like i wanted

paper echo Jun 28, 2020, 9:03 PM

#

The class has to know about the decorator at object instantiation time

pliant tusk Jun 28, 2020, 9:03 PM

#

def set(name):
  class Dec:
    ...
  return Dec

narrow kettle Jun 28, 2020, 9:04 PM

#

like that code up there works for what i need, i just would need to have a decorator per event

#

how would that work chil?

flat gazelle Jun 28, 2020, 9:04 PM

#

could do that with __getattr__

pliant tusk Jun 28, 2020, 9:05 PM

#

@narrow kettle you can return a non-initialized class from the function so customize the class by event name

#

and just return the class

narrow kettle Jun 28, 2020, 9:05 PM

#

basically if i make it a general decorator for all events then i need a way to get the acutal method reference from the decorator

pliant tusk Jun 28, 2020, 9:05 PM

#

and do whatever instance hacks inside that class

narrow kettle Jun 28, 2020, 9:05 PM

#

i want zero name conventions

#

thats the kicker

pliant tusk Jun 28, 2020, 9:05 PM

#

wait so what result do you want?

narrow kettle Jun 28, 2020, 9:06 PM

#

ya it would be easy if i could just make it so the name of the event has to match the method name

paper echo Jun 28, 2020, 9:06 PM

#

@narrow kettle look at how its done in attrs and discordpy

narrow kettle Jun 28, 2020, 9:06 PM

#

what file is that in

final whale Jun 28, 2020, 9:07 PM

#

discord/ext/commands/cog.py

narrow kettle Jun 28, 2020, 9:07 PM

#

wait so what result do you want?
i want the flexibilty to do something like this ```py
class SomeService:
@messenger.Set('some_event_name')
def some_random_name(self):
pass

#

i can do this rn

#

class SomeService:
  @messenger.some_event_name
  def some_random_name(self):
    pass

#

but if i did that id want to generator all the event decorators instead of typing them

#

hence the generator question

#

ahh ok, this d.py thing might be what i want

#

hmm

final whale Jun 28, 2020, 9:10 PM

#

maybe with composition

narrow kettle Jun 28, 2020, 9:10 PM

#

but out of curisoity IS there a good way to generate python code?

#

that can then be referenced later

pliant tusk Jun 28, 2020, 9:11 PM

#

i mean you can generate AST and compile it/convert it to source code

#

and you can use eval

#

but there isnt really any good way

narrow kettle Jun 28, 2020, 9:11 PM

#

does eval add those types to the current running assembly

pliant tusk Jun 28, 2020, 9:12 PM

#

exec would

narrow kettle Jun 28, 2020, 9:12 PM

#

interesting

#

ill look into this return the decorator class ty

final whale Jun 28, 2020, 9:39 PM

#

so far, here's what I could come with

#

import functools
import typing

Result = typing.Union[typing.Any, Exception]

class EventHandler:

    def event_handler(self, name: str = None, /):

        def wrapper(func: typing.Callable):

            handler_name = name or func.__name__

            if curr_handlers := getattr(self, handler_name, None):
                curr_handlers.append(func)

            else:
                setattr(self, handler_name, [func])

            @functools.wraps(func)
            def wrapped(*args, **kwargs):
                return func(*args, **kwargs)

            return wrapped

        return wrapper

    @staticmethod
    def _call_handlers(handlers: list, *args, **kwargs) -> typing.Generator[Result, None, None]:
        for handler in handlers:
            try:
                yield handler(*args, **kwargs)
            except Exception as error:
                yield error

    def dispatch(self, event_name: str, *args, **kwargs):

        handlers = getattr(self, event_name)  # might raise

        return tuple(self._call_handlers(handlers, *args, **kwargs))

narrow kettle Jun 29, 2020, 12:30 AM

#

just saw this @final whale i appreciate it ill take a look

grave jolt Jun 29, 2020, 6:23 AM

#

@paper socket This is not a help channel, please read the channel description. If you want hep with a specific question, check out #❓｜how-to-get-help

#

Personally, I don't see why a chatbot is better than a wiki-like page

#

Python is often used for chatbots, so if you know Python, use it.

#

There is no single framework for bots since they work very differently on different platforms. You can search for a Python library for your specific platform.

#

@final whale I would rather do name: str = "", or name: Optional[str] = None. I'm not very fond of type annotations everywhere (it's obvious that name is a string, and func is a callable), but if you are, make them accurate.

#

Also -- what's the point of the wrapped function? You can just return func.

#

Another possible issue: name clash. handler_name could clash with some other attribute, so maybe put the handlers in a _event_handlers attribute that would be a dict.

cloud crypt Jun 29, 2020, 7:49 AM

#

I am still with None-aware operators in my mind lemon_sentimental

red solar Jun 29, 2020, 7:56 AM

#

oh we changed the channel name

#

lol did you guys see what went down in python-ideas mailing list?

true hollow Jun 29, 2020, 8:05 AM

#

If "explicit is better than implicit", why there is no @instancemethod, for example?

cloud crypt Jun 29, 2020, 8:06 AM

#

because it is default behavior I guess

red solar Jun 29, 2020, 8:08 AM

#

explicit is better than implicit if implicit could be ambiguous

#

which in this case it's not

cloud crypt Jun 29, 2020, 8:11 AM

#

there should be one — and preferable only one — obvious way to do it

#

macro_def ignore_error($line, $errors):
    try:
        return $line
    except $errors:
        return

x = ignore_error!(1 / 0, ZeroDivisionError)  # will be None``` my brain is throwing weird ideas now ![lemon_thinking](https://cdn.discordapp.com/emojis/680222129744380010.webp?size=128 "lemon_thinking")

true hollow Jun 29, 2020, 8:15 AM

#

are you rusting?

hazy anchor Jun 29, 2020, 8:15 AM

#

Oxidising :D

cloud crypt Jun 29, 2020, 8:21 AM

#

rusting very

#

def _ignore_error_fn():
    try:
        return 1 / 0
    except ZeroDivisionError:
        return

x = _ignore_error_fn()``` can get translated to this I guess

true hollow Jun 29, 2020, 8:26 AM

#

rusting in #internals-and-peps flush

cloud crypt Jun 29, 2020, 8:26 AM

#

it has no practical use in python imho

#

owoAttacc

final whale Jun 29, 2020, 8:27 AM

#

Thank you for the suggestions, will fix @grave jolt

cloud crypt Jun 29, 2020, 8:27 AM

#

who 👀

#

ah

#

I see

red solar Jun 29, 2020, 9:14 AM

#

you know how _ prefix makes variables private in the sense that you shouldn't access them and if you do and break something it's your fault...

#

does the same apply to dunder methods?

flat gazelle Jun 29, 2020, 9:18 AM

#

if you mean manually calling dunders, it should be avoided, but is needed for things like __debug__, __file__, __name__, ...

red solar Jun 29, 2020, 9:19 AM

#

ok but someone manually calling __new___ and __init__?

flat gazelle Jun 29, 2020, 9:20 AM

#

generally a bad idea unless you are doing super().__init__. Sometimes needed when doing more complex with classes

red solar Jun 29, 2020, 9:21 AM

#

ok, so no one should be calling them in a way that's semantically different than using standard syntax like super().__init__ and Class()?

flat gazelle Jun 29, 2020, 9:23 AM

#

well, shouldn't is a strong word. Abusing the object system in python is pretty common for various libraries, but if you are just working with normal, not horribly mangled python objects, you should just use Class()

languid dagger Jun 29, 2020, 9:36 AM

#

super().__init__ and Class() both do different things so I wouldn't try equate them

tawdry gulch Jun 29, 2020, 9:37 AM

#

Class() calls new as well right?

flat gazelle Jun 29, 2020, 9:37 AM

#

they are entirely different

tawdry gulch Jun 29, 2020, 9:37 AM

#

Darn, that new is supposed to be dunder*

languid dagger Jun 29, 2020, 9:37 AM

#

You should use builtins to call the dunder methods where available

lst = [1, 2, 3]
s = str(lst)  # good
s = lst.__str__()  # bad```

#

Class() calls __call__ of the Class type and then __new__ and then __init__ and possibly others (for example dataclasses have a __post_init__)

red solar Jun 29, 2020, 9:40 AM

#

ohhh that's what __call__ does

#

was very confused, cuz in c++, you're not allowed to have static operator()(...)

languid dagger Jun 29, 2020, 9:44 AM

#

You can define your own __call__ for instances

class A:
    def __call__(self, x, y):
        return x + y

>>> a = A()
>>> a(1, 2)
3```

red solar Jun 29, 2020, 9:48 AM

#

but not as a classmethod?

flat gazelle Jun 29, 2020, 9:48 AM

#

no. You need a metaclass for that afaik

red solar Jun 29, 2020, 9:54 AM

#

ah ok so it is like c++

long pulsar Jun 29, 2020, 10:11 AM

#

I think this is more of an opinion question so I don't want to post it in one of the help channels.
What I'm doing atm is: I start from a list of keys, these are also the keys in my database. I have a data object in which I store information, and that contain some helper methods like representaion and serialization.
Then I have a lookup objects. The reason I want to maintain state is that it can be called several times during the overall process and I can often resuse the results. Also yeah, just felt cleaner to me.
(below you find a minimal example)

However I like being explicit. And for me that also means I like to return things. In gerneral none of the methods would have to return, since I'm always mutating objects. But I could come up with one in each case.What do you think?

#

class MyDataClass:
    def __init__(self, key, datum01=None, datum02=None):
        self.key = key
        self.datum01 = datum01 
        self.datum02 = datum02
    
    def to_json(self):
        return json.dumps(self, default=lambda o: o.__dict__, sort_keys=True,
                          indent=4)

def get_data_from_db(keys):
    samp = [['001', 'foo', 666], ['002', '#googleMurrayBookchin', 42], ['003', 'barfooo', 2]]
    return samp

class MyLookupClass:
    def __init__(self, config):
        self.lookup_dict = {}
        self.config = config

    def prepare_lookup(self, data_objects: List[MyDataClass]):
        keys = (obj.key for obj in data_objects)
        for key in keys:
            self.lookup_dict[key] = ''

    def populate(self):
        db_response = get_data_from_db(self.lookup_dict.keys())
        for row in db_response:
            self.lookup_dict[row[0]] = row[1:]

    def update_objects(self, data_objects: List[MyDataClass]):
        for obj in data_objects:
            data = self.lookup_dict[obj.key]
            obj.datum01, obj.datum02 = data[1], data[2]


from look_up import MyLookupClass, MyDataClass
def this_happens_in_flask(keys: List[str]):
    config = {}
    look_up = MyLookupClass(config)
    data_obj = [MyDataClass(key) for key in keys]
    look_up.prepare_lookup(data_obj)
    look_up.populate()
    look_up.update_objects(data_obj)

flat gazelle Jun 29, 2020, 10:26 AM

#

that seems quite overcomplicated. Why does one need to call 4 functions to get the data. I would just do

class LookUp:
    def __init__(self, keys):
        self._lookup = {}
        self.keys = keys
    def get_object(self, key):
        if key not in self.keys:
            raise KeyError
        return self.lookup[key]
    @property
    def lookup(self):
        if not self._lookup:
            self._lookup = {key: MyDataClass(key, *data) for key, *data in get_data_from_db(self.keys)}
        return self._lookup
def this_happens_in_flask(keys: List[str]):
    lookup = MyLookupClass(keys)
    results = lookup.lookup
```unless there are other requirements which mandate having so many functions for fetching data

long pulsar Jun 29, 2020, 10:42 AM

#

So yes there is a bit more to it of course. Populate for example also does some postprocessing on the data. And the update process is more complicated. And it's more about the general question not the application here. Imagine the complexity is warranted. Would you explicitly return or mutate?

Also I've recently watched Brandon Rhodes on Clean Architecture. And I kinda tried to follow the priciples by not burrying my I/O opperation. And the person I talk most with about coding is a reactive kotlin programmer that follows that shit pretty zealously lol

red solar Jun 29, 2020, 11:43 AM

#

@raven ridge (or anyone else who does c stuff), you think 3 pointers worth of indirection is too much for a python function call? (like atomic_compare_exchange_strong)

gloomy rain Jun 29, 2020, 2:32 PM

#

@thick topaz This channel is for indepth discussion about the Python language. If you want help or feedback, check out #❓｜how-to-get-help

thick topaz Jun 29, 2020, 2:32 PM

#

oh ok

long pulsar Jun 29, 2020, 2:35 PM

#

@gloomy rain since you are here, would you say my question if in depth enogh or shoudl I also rather ask in a help channel.

gloomy rain Jun 29, 2020, 2:36 PM

#

I think at face value it seems more like a help channel situation.

#

If you need help in general, I think it's better to use a help channel.

#

If you just want to discuss something related to the Python language, this channel is more suitable.

#

But it's a bit of a gray area.

#

You're asking for a code review here basically.

unkempt rock Jun 29, 2020, 2:45 PM

#

Hi. I want to count the possible multiples of 3 in range 50 to 500. How can I do that?(I'm a beginner so the simplest way possible please )

gloomy rain Jun 29, 2020, 2:46 PM

#

@unkempt rock This channel is for indepth discussion about the Python language. If you want help or feedback, check out #❓｜how-to-get-help

slim wing Jun 29, 2020, 2:47 PM

#

how did Guido created python???

#

and is it really very easy creating a language as such ?

gloomy rain Jun 29, 2020, 2:48 PM

#

He presumably wrote the first draft of an implementation in C. No, implementing a practically useful programming language is not easy.

slim wing Jun 29, 2020, 2:48 PM

#

ooo

undone hare Jun 29, 2020, 3:06 PM

#

For the compiling part, Guido mostly followed the parser and lexical analyser implementation outlined in the dragon book, if you are interested

rugged lake Jun 29, 2020, 3:07 PM

#

how did he even have the effort to do it

narrow kettle Jun 29, 2020, 3:08 PM

#

Same way anyone has the effort to write a language

rugged lake Jun 29, 2020, 3:09 PM

#

how to have effort

narrow kettle Jun 29, 2020, 3:09 PM

#

Same way as anything else you work hard at 🤷‍♀️

true hollow Jun 29, 2020, 3:16 PM

#

I doubt the first python code was executed the first day of its developent

#

Cresting a programming language (the syntax and rules) is easy, just have imagination and done

#

But creating the interpreter/compiler is hard work

#

You need to scan if the syntax is okay, and then parse it to convert it to machine code or bytecode

narrow kettle Jun 29, 2020, 3:17 PM

#

Ehh, tbh the hard part is the syntax and the idea lol

#

Basic Parsers and lexers aren’t THAT hard

#

And there’s a million resources on how to do them

#

The hard part is having a consistent idea for what you want

true hollow Jun 29, 2020, 3:18 PM

#

and btw to convert it to machine code you need assembly knowledge

#

how are you supposed to write a C compiler from scratch without assembly knowledge

#

welp, with python is different

#

the result is bytecode

narrow kettle Jun 29, 2020, 3:19 PM

#

theres many different ways to approach such things

#

some more difficult then others

#

but the actual coherent idea/spec is the hard part

#

the other stuff is tedious but can be learned

true hollow Jun 29, 2020, 3:20 PM

#

python is at the same way powerful but sometimes inconsistent

narrow kettle Jun 29, 2020, 3:21 PM

#

its not perfect no, no language is. especially one as old as python

#

things change, ideas evolve

true hollow Jun 29, 2020, 3:24 PM

#

pep8: classes must start with uppercase and follow camel case
str, int, or bool go brr brrr

narrow kettle Jun 29, 2020, 3:25 PM

#

or float

spice pecan Jun 29, 2020, 3:25 PM

#

builtins go brr

narrow kettle Jun 29, 2020, 3:25 PM

#

but that differentiates them as primitives persay

#

same in C#

#

int is just a alias for Int32

spice pecan Jun 29, 2020, 3:27 PM

#

I think lowercase in built-in class names is fine, the only gripe I have is some inconsistencies in methods/dunders

#

In case of str, most if not all method names are just joined, while other classes tend to have underscores separating the words

#

Similarly, some dunders just join the words, like __getattribute__, while newer ones seem to use underscores, like __set_name__ and __class_getitem__

peak spoke Jun 29, 2020, 3:32 PM

#

That's mostly because they came before the style guides or depend on something that doesn't follow python's naming

spice pecan Jun 29, 2020, 3:34 PM

#

I understand why it's like that, and I don't mind it that much, but it's still a little annoying at times

flat gazelle Jun 29, 2020, 3:43 PM

#

It would probably also be confusing to beginners which builtins are capitalized and which are not

remote lantern Jun 29, 2020, 3:44 PM

#

isn't python's variable naming snake_case?

flat gazelle Jun 29, 2020, 3:44 PM

#

ye, but str, int, type, bool, ... is a class, which follow PascalCase

remote lantern Jun 29, 2020, 3:44 PM

#

interesting

#

functions are pascalcase too, right?

flat gazelle Jun 29, 2020, 3:45 PM

#

everything but constants and classes is snake_case

remote lantern Jun 29, 2020, 3:45 PM

#

ah

#

i know constants are in allcaps

flat gazelle Jun 29, 2020, 3:46 PM

#

functions, modules, attributes, methods, variables, packages are all snake_case

remote lantern Jun 29, 2020, 3:46 PM

#

so it would seem

#

PEP8 is a handful

true hollow Jun 29, 2020, 4:22 PM

#

logging module flashbacks judoon

paper echo Jun 29, 2020, 4:34 PM

#

why don't multiprocessing.Process objects support the context manager protocol

red solar Jun 29, 2020, 4:37 PM

#

i thought lock supports it?

#

not sure how the process would support it tho?

paper echo Jun 29, 2020, 4:51 PM

#

process has a close method

#

so you'd expect it to have enter and exit

spark magnet Jun 29, 2020, 4:54 PM

#

@paper echo i don;'t have an answer, but: contextlib.closing() could help

paper echo Jun 29, 2020, 4:54 PM

#

yep, thats a handy one

stable grail Jun 29, 2020, 6:24 PM

#

@paper echo you can also look into this

#

!d multiprocessing.managers.SyncManager

fallen slateBOT Jun 29, 2020, 6:24 PM

#

`multiprocessing.managers.SyncManager`

class multiprocessing.managers.SyncManager```
A subclass of [`BaseManager`](#multiprocessing.managers.BaseManager "multiprocessing.managers.BaseManager") which can be used for the synchronization of processes. Objects of this type are returned by `multiprocessing.Manager()`.

Its methods create and return [Proxy Objects](#multiprocessing-proxy-objects) for a number of commonly used data types to be synchronized across processes. This notably includes shared lists and dictionaries.

`Barrier`(*parties*[, *action*[, *timeout*]])[](#multiprocessing.managers.SyncManager.Barrier "Permalink to this definition") Create a shared [`threading.Barrier`](threading.html#threading.Barrier "threading.Barrier") object and return a proxy for it.

New in version 3.3.

`BoundedSemaphore`([*value*])[](#multiprocessing.managers.SyncManager.BoundedSemaphore "Permalink to this definition") Create a shared [`threading.BoundedSemaphore`](threading.html#threading.BoundedSemaphore "threading.BoundedSemaphore") object and return a proxy for it.... [read more](https://docs.python.org/3/library/multiprocessing.html#multiprocessing.managers.SyncManager)

paper echo Jun 29, 2020, 8:30 PM

#

huh

#

this looks like it's meant more for e.g. wrapping non-multiprocessing-aware things, no?

#

e.g. sharing a value or array or threading.Lock across processes

unkempt rock Jun 29, 2020, 9:54 PM

#

Does close actually do anything tho?

paper echo Jun 29, 2020, 10:06 PM

#

evidently its not necessary

languid dagger Jun 29, 2020, 10:32 PM

#

Is there a reason you can't join?

paper echo Jun 29, 2020, 10:34 PM

#

@languid dagger they wanted to run 2 processes then kill both after one of them finished

languid dagger Jun 29, 2020, 10:48 PM

#

Maybe you want concurrent.futures.ProcessPoolExecutor so you can wait for futures

radiant fulcrum Jun 29, 2020, 10:51 PM

#

tbf if its not cpu or io bound async might be better also

paper echo Jun 30, 2020, 12:31 AM

#

@languid dagger can you wait for "first completed" with the executor?

#

i know you can with asyncio

languid dagger Jun 30, 2020, 12:32 AM

#

https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.wait

#

I believe that works, I haven't used concurrent.futures

paper echo Jun 30, 2020, 12:41 AM

#

ahhh nice

#

its the same as asyncio.wait

#

very useful

unkempt rock Jun 30, 2020, 5:55 AM

#

ummmm

clever schooner Jun 30, 2020, 6:59 AM

#

Hey, I got a problem with a small double for loop problem. Im getting a "float" object not iterable error. However, I have no idea what is wrong. Here is what I have ``` for i in range (n):
avg += x[i]
avg*=(1/n)

m=[2,3,4]
new_m=[]
for j in m:
    for i in range(11):
        m+=(x[i]-avg)**j
    m*=(1/n)
new_m= new_m.append(m)```

#

with the following error.

📎 unknown.png

#

this being the eq I want to perform

📎 unknown.png

#

If I could get some help that would be much appreciated. Thank you in advance

remote lantern Jun 30, 2020, 7:02 AM

#

you're trying to iterate through m (for j in m)

#

but you're adding to m

#

so is it an iterable or not

#

maybe try naming your variables something less confusing?

feral marsh Jun 30, 2020, 7:02 AM

#

oh yeah

#

you forgot to do the ()

clever schooner Jun 30, 2020, 7:14 AM

#

brackets didnt change anything in regards to the error :/

#

@remote lantern it seems like I understood what u mean but It came up with a different error later down

remote lantern Jun 30, 2020, 7:19 AM

#

hmm

clever schooner Jun 30, 2020, 7:19 AM

#

📎 unknown.png

remote lantern Jun 30, 2020, 7:19 AM

#

that sounds... concerning

clever schooner Jun 30, 2020, 7:19 AM

#

Ill send u the error and the problem 1 sec

#

📎 unknown.png

remote lantern Jun 30, 2020, 7:20 AM

#

it means something's returning None

#

RemThink

#

hmm

clever schooner Jun 30, 2020, 7:20 AM

#

📎 unknown.png

#

this is what I was trying to perform

remote lantern Jun 30, 2020, 7:21 AM

#

strange

clever schooner Jun 30, 2020, 7:22 AM

#

do u have any idea?

remote lantern Jun 30, 2020, 7:29 AM

#

i think it's the line new_m = new_m.append(m)

#

append() returns None

#

so when you try to give that value to new_m itself i think new_m turns into a None object?

#

that's my best guess

#

just do new_m.append(m) and it should work

#

also may i recommend learning about list comprehensions

#

very useful and may compact your code

#

https://www.youtube.com/watch?v=3dt4OGnU5sM

YouTube

Corey Schafer

Python Tutorial: Comprehensions - How they work and why you should ...

Python comprehensions are a very natural and easy way to create lists, dicts, and sets. They are also a great alternative to using maps and filters within python. If you are using maps, filters, or for loops to create your lists, then most likely you could and should be using ...

▶ Play video

clever schooner Jun 30, 2020, 7:34 AM

#

just do new_m.append(m) and it should work
@remote lantern same error came up :/

#

nvm i got it

#

indentation error

grizzled vigil Jun 30, 2020, 8:30 AM

#

@clever schooner @remote lantern For future reference, such conversations are better placed in the help channels, rather than #python-language. As per the description, this channel is intended for discussion of advanced language features, PEPs, etc; not for providing troubleshooting assistance.

remote lantern Jun 30, 2020, 8:30 AM

#

will do

#

was only talking here because chat seemed dead and they needed help

grizzled vigil Jun 30, 2020, 8:31 AM

#

That's okay. If it occurs again, you can redirect them to a help channel, then have them @ mention you if you are willing and able to assist with the problem.

remote lantern Jun 30, 2020, 8:31 AM

#

alright

unkempt rock Jun 30, 2020, 9:29 AM

#

Okay so i need some help regarding scheduling my tasks
so at first i have one ,

my_list = ['94230', '40737', '06959', '62168']

now i want to print the first value of my_list....which is '94230'
the i want to keep the same code for 2 days/48hrs then i want to delete
the first item of the list which is '94230' then print the second item
of list which is '40737' and keep on following the same pattern....

so how should i do that?

red solar Jun 30, 2020, 9:30 AM

#

a loop with time.sleep()?

#

but also not the right channel (i feel the channel name might be misleading)

unkempt rock Jun 30, 2020, 9:32 AM

#

@red solar its regarding python stuff right?

brave badger Jun 30, 2020, 9:33 AM

#

Discussion about these concepts. I think your question may be suited better for one of the topical channels or a help channel.

📎 unknown.png

unkempt rock Jun 30, 2020, 9:34 AM

#

@brave badger Sorry didnt read the pins

quick elbow Jun 30, 2020, 10:15 AM

#

I want to make a OS with Python, this will be a simple OS, like ms-DOS (Maybe more simple lol). Can I do it with Python?

true hollow Jun 30, 2020, 10:16 AM

#

@quick elbow with cpython definitely not

#

also if you want to make an os like msdos you must learn x86 assembly

#

please visit these two websites
https://osdev.wiki/
https://wiki.osdev.org/

quick elbow Jun 30, 2020, 10:17 AM

#

is it hard?

#

x86 Assembly*

true hollow Jun 30, 2020, 10:17 AM

#

for me nope

quick elbow Jun 30, 2020, 10:17 AM

#

I just want to make a ultra simple os

true hollow Jun 30, 2020, 10:17 AM

#

https://github.com/pritamzope/os simple oses

open trout Jun 30, 2020, 10:18 AM

#

TempleOS 👼

true hollow Jun 30, 2020, 10:18 AM

#

also wdym by "simple os"

#

just a hello world?

quick elbow Jun 30, 2020, 10:18 AM

#

not just hello world

#

I was making a .py for this os

true hollow Jun 30, 2020, 10:19 AM

#

filesystem, keyboard input, screen output, api?

#

btw you can't create an os with cpython

quick elbow Jun 30, 2020, 10:19 AM

#

hmm

#

wait lemme look to assembly

true hollow Jun 30, 2020, 10:19 AM

#

@quick elbow *x86 assembly

#

there are many assemblies

#

powerpc, arm, x86, mips, 6502, jvm

#

AVR, RISC-V...

#

m68k...

#

w8 this is offtopic flush

quick elbow Jun 30, 2020, 10:20 AM

#

my project was:
it has a simple mail system that can send mail to gmail/outlook . blah blah...

#

and

true hollow Jun 30, 2020, 10:21 AM

#

thats not simple lol

quick elbow Jun 30, 2020, 10:21 AM

#

it dont have a ui

#

thats not simple lol
@true hollow I did it with python in vscode 🤦‍♂️

true hollow Jun 30, 2020, 10:21 AM

#

you need to implement:
• network driver
• some keyboard driver and screen driver
• and then create the mail client

#

oh lol

open trout Jun 30, 2020, 10:21 AM

#

"just a simple OS" famous last words

true hollow Jun 30, 2020, 10:22 AM

#

no os is simple lol

#

I think you mean with simple os "a basic bootloader"

quick elbow Jun 30, 2020, 10:22 AM

#

ok x86 isnt so easy to learn..

📎 unknown.png

true hollow Jun 30, 2020, 10:22 AM

#

that's not hard lol

#

Basically move data to registers and trigger some interrupt

quick elbow Jun 30, 2020, 10:23 AM

#

if I can create a msdos like OS I will buy a soooo old computer lol

true hollow Jun 30, 2020, 10:23 AM

#

you don't to lol

#

you just need an x86 computer with bios

quick elbow Jun 30, 2020, 10:23 AM

#

is x86 is byte?

true hollow Jun 30, 2020, 10:23 AM

#

what?

quick elbow Jun 30, 2020, 10:23 AM

#

waitwait

#

my english bad sorry

true hollow Jun 30, 2020, 10:24 AM

#

May we move to DMs and let moderators purge this offtopic conversation?

quick elbow Jun 30, 2020, 10:24 AM

#

gogo dm

unkempt rock Jun 30, 2020, 11:29 AM

#

Hey, can anyone tell how to keep bot connected forever?

#

Cuz whenever close the application in which python I running, bot goes offline

gloomy rain Jun 30, 2020, 11:30 AM

#

@unkempt rock This channel is for indepth discussion of the Python language. If you need help, you should check out #❓｜how-to-get-help.

unkempt rock Jun 30, 2020, 11:31 AM

#

Oh ok

#

Thx

subtle pike Jun 30, 2020, 11:43 AM

#

@quick elbow sure you can, you will need to:

implement python yourself in C or assembly
implement a PE/ELF loader in C or assembly
implement your own executable format then write a compiler mod to compile the exiting CPython source into it (you will need to account for expected platform resources like threading)

#

the issue is that python, itself, isn't granular enough and relies on a lot of resources behind the scenes

#

for example, python heavily relies on a garbage collector which requires a heap, which requires a memory manager, etc

#

@true hollow assembly itself isn't hard but to implement an actual OS is

#

there is a reason why each instruction listing in the intel manuals has barely a couple sentences describing it but has entire volumes dedicated to memory management or execution modes

#

@unkempt rock ?

flat gazelle Jun 30, 2020, 12:33 PM

#

It would be much easier to lean a language more suited to OS dev (C, go, possibly rust, zig, odin) than to make an OS in python.

quick elbow Jun 30, 2020, 12:38 PM

#

@subtle pike thanks for info

unkempt rock Jun 30, 2020, 1:26 PM

#

@true hollow why are you trying to convince people x86 is easy 😂

true hollow Jun 30, 2020, 1:26 PM

#

because it is

#

modern programmers portrait is as a hell language only for people with 200 iq

flat gazelle Jun 30, 2020, 1:27 PM

#

getting things done is ASM is more tedious than difficult

true hollow Jun 30, 2020, 1:27 PM

#

depends what are you doing

#

if you are creating a python module, well, good luck

flat gazelle Jun 30, 2020, 1:27 PM

#

because you do not have cheap abstraction that other languages give you

unkempt rock Jun 30, 2020, 1:28 PM

#

Doing stuff in asm is tedious, and you need to know a fair amount and can’t make any mistakes (python is significantly easier in that regard) - doing stuff well in asm takes a whole lot of in depth knowledge of your target architecture

#

Maybe you could say some RISC ISAs are simple....

#

But I wouldn’t say that about x86

true hollow Jun 30, 2020, 1:28 PM

#

welp for me x86 assembly is easy
gimme docs and what i need to do and done

unkempt rock Jun 30, 2020, 1:29 PM

#

The docs are the huge book that is the intel developer manual

#

Right of the bat that’s significantly harder to read than python docs

#

That and agner’s stuff

true hollow Jun 30, 2020, 1:29 PM

#

read x86-64 amd docs instead

unkempt rock Jun 30, 2020, 1:30 PM

#

Yeah doesn’t look significantly simpler

golden imp Jun 30, 2020, 7:28 PM

#

what are people's thought on the overrides library, or explicit overrides in general?

unkempt rock Jun 30, 2020, 8:41 PM

#

Seems pretty cool

clever skiff Jun 30, 2020, 9:07 PM

#

Someone indicates a free Python OOPs concepts course, please? Thanks

#

Sorry for my english

magic python Jun 30, 2020, 9:40 PM

#

@clever skiff wrong channel

#

!resources

fallen slateBOT Jun 30, 2020, 9:41 PM

#

Resources

The Resources page on our website contains a list of hand-selected learning resources that we regularly recommend to both beginners and experts.

narrow kettle Jun 30, 2020, 10:21 PM

#

not the correct channel

grave jolt Jun 30, 2020, 10:25 PM

#

@royal cliff This is not a help channel (see the channel description). Please check out #❓｜how-to-get-help

boreal umbra Jul 1, 2020, 4:40 AM

#

Why are the types returned by keys, values, and items for dict not lists?

raven ridge Jul 1, 2020, 4:41 AM

#

Making them lists would result in slower code because of the extra copying

#

Plus they have a feature lists don't, they update as the underlying container does.

boreal umbra Jul 1, 2020, 4:42 AM

#

I don't understand the added utility of them updating along with the dict itself, since you can call those methods at any time

#

Unless they're just a window into the data structure and don't actually cause anything new to be created

charred wagon Jul 1, 2020, 4:43 AM

#

Yes, that's what they are afaik

boreal umbra Jul 1, 2020, 4:43 AM

#

And the fact that they have the external behavior of self-updating is a side effect

#

In that case, why are they methods rather than at the ivy?

#

Attributes?

charred wagon Jul 1, 2020, 4:46 AM

#

I don't know

#

It could be a property I guess

boreal umbra Jul 1, 2020, 4:46 AM

#

Or maybe those methods have arguments that I don't know about.

charred wagon Jul 1, 2020, 4:46 AM

#

But they didnät exist back then

boreal umbra Jul 1, 2020, 4:47 AM

#

Did the code underlying properties exist though?

#

I think I remember reading that properties are a utilization of some language feature where you have untouchable objects that implicitly affect what the dot operator does for classes that use it.

charred wagon Jul 1, 2020, 4:51 AM

#

Not sure, I suppose that is a good point. They're implemented in C so they wouldn't need to depend on the public properties API

#

But I think I misunderstood your question

#

Yeah, I don't really see why the view would need to be re-created each time if it's dynamically going to update. It could just be created once and stored as an attribute

raven ridge Jul 1, 2020, 4:54 AM

#

In that case, why are they methods rather than at the ivy?
The methods predate the "view" behavior. Previously they did return lists. https://docs.python.org/2/library/stdtypes.html#dict.keys etc

boreal umbra Jul 1, 2020, 4:54 AM

#

I didn't get that impression based on your answer

charred wagon Jul 1, 2020, 4:54 AM

#

Ah well that explains it all

#

Backwards compat then

boreal umbra Jul 1, 2020, 4:54 AM

#

Makes sense.

swift imp Jul 1, 2020, 4:54 AM

#

Returning lists would be inefficient

#

That's why

#

Plain and simple

boreal umbra Jul 1, 2020, 4:55 AM

#

I don't know that it's plain and simple

raven ridge Jul 1, 2020, 4:55 AM

#

I think I remember reading that properties are a utilization of some language feature where you have untouchable objects that implicitly affect what the dot operator does for classes that use it.
@boreal umbra You're describing "descriptors"

boreal umbra Jul 1, 2020, 4:55 AM

#

Since lists are the primary structure for ordered data

raven ridge Jul 1, 2020, 4:55 AM

#

yes, but copying is slow. It is that simple.

charred wagon Jul 1, 2020, 4:55 AM

#

They could cache the view objects but presumably they don't since it's not worth it.

boreal umbra Jul 1, 2020, 4:56 AM

#

Right, but most python users don't know how the language is implemented, so it wouldn't be immediately obvious that using lists would be problematic in this case.

swift imp Jul 1, 2020, 4:56 AM

#

What's faster in C, passing an entire array or passing a pointer to that array and an int indicating the length?

raven ridge Jul 1, 2020, 4:56 AM

#

https://docs.python.org/3.0/whatsnew/3.0.html#views-and-iterators-instead-of-lists describes the change in terms of efficiency.

swift imp Jul 1, 2020, 4:57 AM

#

It's really that simple

raven ridge Jul 1, 2020, 4:58 AM

#

https://www.python.org/dev/peps/pep-3106/#introduction also says that the motivation was to return a lighter weight object. Just performance.

Python.org

PEP 3106 -- Revamping dict.keys(), .values() and .items()

The official home of the Python Programming Language

charred wagon Jul 1, 2020, 5:00 AM

#

It would be okay if multiple calls to d.keys() (etc.) returned the same object, since the object's only state is the dict to which it refers. Is this worth having extra slots in the dict object for? Should that be a weak reference or should the d_keys (etc.) object live forever once created? Strawman: probably not worth the extra slots in every dict.

#

Neat thanks

boreal umbra Jul 1, 2020, 5:00 AM

#

Well, I'm only objecting to characterizing this as plain and simple from the perspective of those who don't know about or aren't interested in low level implementation details.

raven ridge Jul 1, 2020, 5:01 AM

#

yeah - I agree that it might be non-obvious, but it is "plain and simple" in that the one word answer "efficiency" is correct.

boreal umbra Jul 1, 2020, 5:03 AM

#

But yes, descriptors are what I was thinking of. I've been meaning to learn about those, so thanks for reminding me of the name

#

Wow, 2006

raven ridge Jul 1, 2020, 5:07 AM

#

nedbat pointed to https://nedbatchelder.com/blog/201306/explaining_descriptors.html the other day as an excellent article for learning descriptors.

unkempt rock Jul 1, 2020, 6:38 AM

#

I was wondering if this is correct, about python

📎 unknown.png

flat gazelle Jul 1, 2020, 6:46 AM

#

Probably not, but I can't quite tell what they claim, so it is hard to tell. Python definitely does not do anything other than tokenization key by key though

unkempt rock Jul 1, 2020, 6:55 AM

#

Got some "clear" explaination

📎 unknown.png

flat gazelle Jul 1, 2020, 6:57 AM

#

Python does have an ast which it does use (though linters afaik use a modified one due to comments and other things the default one does not keep). Hell, python gets compiled to bytecode before running.

#

And that compilation is cached for future use to speed up loading

unkempt rock Jul 1, 2020, 6:58 AM

#

the _pycache_?

flat gazelle Jul 1, 2020, 6:58 AM

#

Ye

unkempt rock Jul 1, 2020, 6:58 AM

#

and also, is that person correct?

#

or wrong

flat gazelle Jul 1, 2020, 7:01 AM

#

Wrong from what I can tell. I mean, the translation from tokens (you can see how those get made with the tokenize module) to ast obviously goes over every token. In regards to parsing/compilation python is not all that different from java and some C impls

#

Python does have a grammar, it is somewhere in the docs

unkempt rock Jul 1, 2020, 7:09 AM

#

this guy is hehehaha

📎 unknown.png

#

aint gonna stop xd

#

I am kinda done with this person

#

xd

last pollen Jul 1, 2020, 7:13 AM

#

I'm not quite sure what they mean by "scan the script by each keyword"

flat gazelle Jul 1, 2020, 7:13 AM

#

ye, he clearly has no clue what he is talking about. The python tokenizer is quite normal

last pollen Jul 1, 2020, 7:15 AM

#

and Python's grammar is fully listed here: https://docs.python.org/3/reference/grammar.html

unkempt rock Jul 1, 2020, 7:15 AM

#

Yeah, ok

#

This guy is really trigerring me

#

xd

flat gazelle Jul 1, 2020, 7:16 AM

#

well, the python lexer is a bit irregular due to handling indentation

unkempt rock Jul 1, 2020, 7:16 AM

#

I mean, other than that

#

Indents dont really matter

#

he is like comprehensions suck and idk what not

grizzled vigil Jul 1, 2020, 7:42 AM

#

At some point, it's just better to step away from the conversation when you realize that it's not going anywhere productive.

unkempt rock Jul 1, 2020, 8:18 AM

#

Yeah

#

Thats what I did

#

xd

pseudo patio Jul 1, 2020, 1:31 PM

#

can someone help me

#

Why VS code doesn't read my txt file

#

here , take a look

📎 unknown.png

brave badger Jul 1, 2020, 1:33 PM

#

@pseudo patio If you require help, please refer to #❓｜how-to-get-help as this is not exactly the proper channel for that

boreal umbra Jul 1, 2020, 1:48 PM

#

I have an idea

#

suppose this syntax were legal

#

from typing import Dict, List, * as t

#

Dict and List are brought directly into that namespace, and then the whole module is imported as t

timber osprey Jul 1, 2020, 1:50 PM

#

hey guys

#

new here

boreal umbra Jul 1, 2020, 1:50 PM

#

Hi

timber osprey Jul 1, 2020, 1:50 PM

#

what language should i learn after learning python

#

if i don't want any front end website

boreal umbra Jul 1, 2020, 1:50 PM

#

None. You have won programming by learning Python.

timber osprey Jul 1, 2020, 1:50 PM

#

or website related jobs

#

should i add some c++

#

to strengthen my foundation

flat gazelle Jul 1, 2020, 1:51 PM

#

C++ is interesting, but learning C++ takes about a lifetime

timber osprey Jul 1, 2020, 1:51 PM

#

ooo i see

flat gazelle Jul 1, 2020, 1:51 PM

#

also, go to off topic probably

boreal umbra Jul 1, 2020, 1:51 PM

#

This particular channel is for talking about the Python language itself

timber osprey Jul 1, 2020, 1:51 PM

#

what is c++ mainly used for?

#

oww

#

sorry guys

#

didn't mean it

boreal umbra Jul 1, 2020, 2:00 PM

#

Also I still crave validation for my proposed import syntax, but feel free to trash talk it as well.

flat gazelle Jul 1, 2020, 2:03 PM

#

it would be nice sugar, but I see pretty much no advantage over

from typing import Dict, List
import typing as t
``` Though python could use a bit more terseness, it is quite verbose

boreal umbra Jul 1, 2020, 2:06 PM

#

have you used Java?

flat gazelle Jul 1, 2020, 2:06 PM

#

yes

boreal umbra Jul 1, 2020, 2:06 PM

#

In that light I'm not sure I agree with that assessment about Python's verbosity.

peak spoke Jul 1, 2020, 2:07 PM

#

I'm not sure if introducing the new syntax would be worth it as it's not as explicit, and importing like that is rarely done

boreal umbra Jul 1, 2020, 2:09 PM

#

I guess it's not explicit in the sense that a * isn't self-explanatory, so you'd have to look up what it's doing in that context.

#

though it's not importing anything that isn't explicitly stated.

flat gazelle Jul 1, 2020, 2:10 PM

#

I mean, there are more verbose languages, but we do not call java terse just because COBOL is more verbose. Compared to haskell, ruby, raku, some LISPs, C#, D and JS in some cases even, python is quite inexpressive.

sacred tinsel Jul 1, 2020, 2:10 PM

#

from typing import Dict, List; import typing as t

lemon_swag

boreal umbra Jul 1, 2020, 2:10 PM

#

but I don't want thatttttt

#

@flat gazelle I see what you're saying

peak spoke Jul 1, 2020, 2:11 PM

#

I'd also expect a * to do something different at first, with it being for unpacking or as the star wildcard on imports

sacred tinsel Jul 1, 2020, 2:11 PM

#

do you find yourself importing the module and then something from the module, separately, often?

flat gazelle Jul 1, 2020, 2:11 PM

#

ye, it is quite inconsistent in that, though it is quite intuitive

boreal umbra Jul 1, 2020, 2:11 PM

#

often I want to import the items I plan to use most frequently by name

sacred tinsel Jul 1, 2020, 2:11 PM

#

when I see it I usually just assumed it was 2 people working on the module together and they didnt notice one or the other was already done lol

boreal umbra Jul 1, 2020, 2:12 PM

#

and then I still want the rest of the module

#

I would include from typing import Dict, List, * in the same proposal, which in this case would be the same as from typing import Dict, list; import typing

#

Perl is more terse than Python, but you also have to spend eleven years figuring out what all the shorthands mean 😄

sacred tinsel Jul 1, 2020, 2:13 PM

#

I'm not sure how I'd feel about the star behaving differently from just from typing import *

#

since if you do that you'll already have the Dict and List available right

boreal umbra Jul 1, 2020, 2:14 PM

#

in the syntax I'm thinking of, if you import something explicitly, followed by a star, the star doesn't implicitly import everything

#

it imports the module itself by its own name.

#

which would be confusing, yes

sacred tinsel Jul 1, 2020, 2:15 PM

#

maybe we should just remove star imports and replace them with this behaviour lol

flat gazelle Jul 1, 2020, 2:15 PM

#

honestly, in 99% of the cases, I either use qualified imports or unqulified imports, not both

boreal umbra Jul 1, 2020, 2:15 PM

#

That gets support from me, but we'd have to wait until python 4

sacred tinsel Jul 1, 2020, 2:16 PM

#

I don't recall mixing them intentionally either

boreal umbra Jul 1, 2020, 2:16 PM

#

unless we decide that people who use wildcard imports don't deserve to have their code work

#

which I also support.

#

Anyway I guess I can go to python-ideas but I imagine unless I include lots of caveats, they'll assume I have no design sense and I'll be eaten alive.

undone hare Jul 1, 2020, 4:29 PM

#

In 3.9 you won't have (in most cases) to import typing anyway lemon_swag

red solar Jul 1, 2020, 4:32 PM

#

ooh 🙂

undone hare Jul 1, 2020, 4:32 PM

#

(I'm referring to https://docs.python.org/3.9/whatsnew/3.9.html#pep-585-builtin-generic-types)

red solar Jul 1, 2020, 4:32 PM

#

contributed by Guido

#

ok ig we're getting it lol

#

wait isn't 3.9 out already?

undone hare Jul 1, 2020, 4:33 PM

#

Nope, there only are ~~release candidates~~ betas for now

red solar Jul 1, 2020, 4:34 PM

#

oh ok thank god i have time for 3.10 then

undone hare Jul 1, 2020, 4:35 PM

#

But I mean https://docs.python.org/3.10/whatsnew/3.10.html lemon_pleased

#

They are what's new pages for un-released versions too

hasty thistle Jul 1, 2020, 5:11 PM

#

ooohhh

#

that seems neat

#

oh wow, they finally added lcm to the math module?

red solar Jul 1, 2020, 5:35 PM

#

if c++ can do it, python can do it 🤷

undone hare Jul 1, 2020, 5:40 PM

#

Well, if C can do it CPython can do it lemon_pleased

languid dagger Jul 1, 2020, 5:48 PM

#

It's not that you couldn't do it before, it just wasn't part of the stdlib

boreal umbra Jul 1, 2020, 5:58 PM

#

@undone hare so basically the builtins are getting __class_getitem__?

undone hare Jul 1, 2020, 5:59 PM

#

Yes, among other things

#

!pep 585

fallen slateBOT Jul 1, 2020, 5:59 PM

#

**PEP 585 - Type Hinting Generics In Standard Collections**

Link

Status

Accepted

Python-Version

3.9

Created

03-Mar-2019

Type

Standards Track

undone hare Jul 1, 2020, 5:59 PM

#

Here is the related PEP with the implementation details lemon_pleased

grand field Jul 1, 2020, 6:12 PM

#

Hey. Just a heads-up. HumbleBundle is having nice sales on Python courses
https://www.humblebundle.com/software/python-programming-software?partner=limitedtimeoffer

Humble Bundle

Humble Software Bundle: Learn Python Programming with PyCharm

Learn Python programming with this learning bundle. Includes PyCharm - 6 months subscription & more. Plus, pay what you want & support charity.

true hollow Jul 1, 2020, 6:56 PM

#

In 3.9 you won't have (in most cases) to import typing anyway
@undone hare is 3.9 released?????

languid dagger Jul 1, 2020, 6:56 PM

#

@grand field That would be better in #python-discussion or an off topic channel, not this one

#

@wary plover Please don't advertise your channel, just wait for help.

undone hare Jul 1, 2020, 7:44 PM

#

@true hollow not yet, only the betas are available right now

true hollow Jul 1, 2020, 7:45 PM

#

I'll consider building one of them

undone hare Jul 1, 2020, 7:49 PM

#

All released and un-released version have a what's new page

#

Even 3.10 has one

#

I'd be surprised if they aren't published binaries for 3.9

radiant fulcrum Jul 1, 2020, 8:48 PM

#

If we assign a attribute to a class

#

say:

#


class FooBar:
  def __init__(self):
    pass
  
  def foo(self):
    pass
  
  def bar(self):
    pass

#

How come we cant then remove these attributes from a instance of it using
delattr

neon tartan Jul 1, 2020, 8:50 PM

#

I don't see attributes? Only methods?

radiant fulcrum Jul 1, 2020, 8:50 PM

#

mhmm

#

yet we can assign the same methods with setattr and remove them like that

#

but then we loose the ability to reference self which annoying

#

It would be nice if we had the ability to modify methods like attributes instead of say doing it with a decorator

neon tartan Jul 1, 2020, 8:52 PM

#

Oh interesting, hmm I'm not sure so you'll have to wait for someone more experienced

north root Jul 1, 2020, 8:53 PM

#

yet we can assign the same methods with setattr and remove them like that
these will not be bound methods

radiant fulcrum Jul 1, 2020, 8:53 PM

#

yeah, which im assuming is also why we cannot reference self which makes sense

peak spoke Jul 1, 2020, 8:54 PM

#

You can bind it when assigning to the instance

#

You can't delete the methods because they don't exist in instances

#

the "nicer" way to bind them when you already have an instance

In [11]: from types import MethodType

In [12]: class MyClass: ...

In [13]: def func(self): return self

In [14]: inst = MyClass()

In [15]: inst.func = MethodType(func, inst)

In [16]: inst
Out[16]: <__main__.MyClass at 0x67ec148>

In [17]: inst.func()
Out[17]: <__main__.MyClass at 0x67ec148>

radiant fulcrum Jul 1, 2020, 8:58 PM

#

oOoh I havent actually seen MethodTypes been used that much

#

that's intersting

rare scaffold Jul 1, 2020, 9:49 PM

#

@grand field is the content good though?

tawny shore Jul 1, 2020, 11:20 PM

#

Yoo

unkempt rock Jul 1, 2020, 11:20 PM

#

How make a thumbnail in the embed

golden imp Jul 1, 2020, 11:25 PM

#

does List become obsolete then?

flat gazelle Jul 1, 2020, 11:26 PM

#

It will stay for backwards compatability, but I think yes

golden imp Jul 1, 2020, 11:26 PM

#

type hints are a wild ride

neon tartan Jul 1, 2020, 11:26 PM

#

Wait, what's changing for type hints?

golden imp Jul 1, 2020, 11:27 PM

#

soon you can do list[int] instead of needing List[int]

neon tartan Jul 1, 2020, 11:27 PM

#

Ah

#

That probably simplifies things

#

It's going to break current typehints on leetcode yaaaaaaaay

flat gazelle Jul 1, 2020, 11:28 PM

#

It won't break anything I would think.

neon tartan Jul 1, 2020, 11:28 PM

#

oh so you just don't have to import from Typing

flat gazelle Jul 1, 2020, 11:28 PM

#

The old typing.List are not removed, though they may be depracated soon

peak spoke Jul 1, 2020, 11:30 PM

#

The PEP mentioned them being deprecated after builtin generics are implemented, but won't raise DeprecationWarning since it's just typing

timid orbit Jul 1, 2020, 11:30 PM

#

having it supported on builtins would be great, yeah

peak spoke Jul 1, 2020, 11:30 PM

#

If you do keep using them from typing for whatever reason then your code will break in the future

swift imp Jul 1, 2020, 11:51 PM

#

Good

#

Because having to do from Typing include * gets annoying as fuck

#

I don't even use mypy but I still like adding type hints for completeness

flat gazelle Jul 1, 2020, 11:52 PM

#

They are a great documentation tool

#

Though I wish people made more type aliases

swift imp Jul 1, 2020, 11:53 PM

#

You can put in whatever u want really

peak spoke Jul 1, 2020, 11:53 PM

#

The builtins are great but I don't think it's that much of a bother as most large projects will have a considerable amount of imports anyway which can be skipped over

swift imp Jul 1, 2020, 11:53 PM

#

Like if I want an arg to be a dataframe I just do pd.DataFrame

#

def func(df:pd.DataFrame)->pd.DataFrame:

#

Clear and concise

unkempt rock Jul 2, 2020, 1:34 AM

#

url_list.insert(y, url_list[y] + 1)

#

is this a correct syntax?

wraith brook Jul 2, 2020, 7:07 AM

#

hello is anyone experienced with django

true hollow Jul 2, 2020, 7:08 AM

#

@wraith brook #web-development 🙂
this channel is to discuss PEPs, language design, the future of this language, etc

wraith brook Jul 2, 2020, 7:08 AM

#

yes i already was talking there sorry

true hollow Jul 2, 2020, 7:08 AM

#

nah don't worry

rare turtle Jul 2, 2020, 11:02 AM

#

If I were to turn a website's API into a library, would it be better to use requests or aiohttp?

sacred tinsel Jul 2, 2020, 11:17 AM

#

depends whether you want it to be asynchronous or not

#

using requests, your library will be easier to use for synchronous applications, whereas using aiohttp will make your library appropriate for async applications

#

it'd probably be very difficult to create something that will "just work" for both

#

usually you have libraries that are either strictly sync, or strictly async

rare turtle Jul 2, 2020, 11:20 AM

#

Fair enough, I get what you mean. Thank you!

sacred tinsel Jul 2, 2020, 11:20 AM

#

yeah no worries - it may be worth looking into whether there already exists a wrapper for the API, and then you can do something that the existing wrapper doesn't do

#

e.g. "while library A already wraps this API, it uses requests and blocks, my implementation is asynchronous and therefore appropriate for async apps" would be a good selling point

rare turtle Jul 2, 2020, 11:21 AM

#

Makes sense, thanks!

true hollow Jul 2, 2020, 12:07 PM

#

async ftw

#

make all your functions be coroutines

rigid tundra Jul 2, 2020, 12:08 PM

#

I have an odd question, when doing a loop with an iterator that is the element and not a numerical incrementor, are you able to change what is in the existing array using that element iterator? Also is there any way to check to see which location that the element iterator is inside of the data structure that you are looping through?

Element:

for i in list:
  // code

Regular:

for i in range(len(list)):
  // code

sacred tinsel Jul 2, 2020, 12:11 PM

#

no it's not possible, if I understand your question correctly

hazy anchor Jul 2, 2020, 12:11 PM

#

enumerate() is one option

sacred tinsel Jul 2, 2020, 12:11 PM

#

>>> nums = [1, 2, 3]
>>> 
>>> for n in nums:
...     n = 0
... 
>>> nums
[1, 2, 3]

hazy anchor Jul 2, 2020, 12:11 PM

#

but only for the second part, knowing where the element came from

sacred tinsel Jul 2, 2020, 12:11 PM

#

the loop binds the value to a new name n

peak spoke Jul 2, 2020, 12:11 PM

#

iterting will create a new reference, with which you´can't access the reference inside what you're iterating over without some provided methods

sacred tinsel Jul 2, 2020, 12:11 PM

#

you can change the value of n, but it doesn't write to the list

#

similarly:

>>> def func(n):
...     n = 0
... 
>>> number = 1
>>> func(number)
>>> number
1

rigid tundra Jul 2, 2020, 12:15 PM

#

Ok, I was wondering how much more magic python had with loops. The majority of my coding experience is with C and Java so coming to a language where looping can be done is different ways was very new. It also still blows my mind that there is no variable scope in methods

#

Thank you

flat gazelle Jul 2, 2020, 12:16 PM

#

Java also has a foreach loop

narrow kettle Jul 2, 2020, 12:21 PM

#

Java has different ways to return an enumerable too

spark magnet Jul 2, 2020, 12:24 PM

#

@rigid tundra what do you mean, "no variable scope in methods"? Methods have local variables.

rigid tundra Jul 2, 2020, 12:27 PM

#

!e

def scope():
  for i in range(1):
    x = 3
  return x
print(scope())

fallen slateBOT Jul 2, 2020, 12:27 PM

#

You are not allowed to use that command here. Please use the #bot-commands channel instead.

flint fractal Jul 2, 2020, 12:27 PM

#

@spark magnet are you actually like a teacher?

spark magnet Jul 2, 2020, 12:27 PM

#

@flint fractal not formally 🙂

flint fractal Jul 2, 2020, 12:28 PM

#

alright

flat gazelle Jul 2, 2020, 12:28 PM

#

those are not methods, but yes, control flow does not have its own scope

spark magnet Jul 2, 2020, 12:28 PM

#

Blocks don't create a new scope, i guess you meant.

rigid tundra Jul 2, 2020, 12:28 PM

#

@spark magnet Blocks?

spark magnet Jul 2, 2020, 12:29 PM

#

the statements inside the "for" loop

flat gazelle Jul 2, 2020, 12:29 PM

#

if 5:
    "this is a block"

spark magnet Jul 2, 2020, 12:29 PM

#

i'm not sure they are actually called blocks. sometimes they are called clauses.

narrow kettle Jul 2, 2020, 12:29 PM

#

those are not methods, but yes, control flow does not have its own scope
A VERY confusing thing when i started

spark magnet Jul 2, 2020, 12:30 PM

#

some people will tell you, once you've learned one or two languages, other languages are easy because you just need to learn the new syntax. those people are wrong 🙂

flint fractal Jul 2, 2020, 12:31 PM

#

facts

#

new language, new stuff to learn

flat gazelle Jul 2, 2020, 12:32 PM

#

it is called body in ast it seems

rigid tundra Jul 2, 2020, 12:33 PM

#

So, humor me on what exactly I said incorrectly

narrow kettle Jul 2, 2020, 12:33 PM

#

I mean once you know one Lang it’s relatively easy to transfer concepts

flat gazelle Jul 2, 2020, 12:33 PM

#

ah, I can tell what you meant. Within a single method, there is no variable scope

#

which is not quite true either

spark magnet Jul 2, 2020, 12:33 PM

#

A method is a function defined within a class. They have their own scope, local variables ,like any function.

narrow kettle Jul 2, 2020, 12:33 PM

#

A bit harder going from paradigm to paradigm

flat gazelle Jul 2, 2020, 12:34 PM

#

def fun():
    a = 5
    def inner():
        a = 8
    inner()
    return a
print(fun()) # 5

wide shuttle Jul 2, 2020, 12:37 PM

#

One think that could help is realizing that a "method" defined within the namespace of a class is just a regular function

#

Basically, this does two things:

def foo():
    pass

#

Python will make sure you've got a function object in memory and you assign a name to that function object

#

While variables work a bit differently in R (copy on assignment), R does show nicely what happens:

#

name <- function(a) {
    print(a)
}

cinder fern Jul 2, 2020, 12:39 PM

#

hello. im learning python since few days and i couldnt understand how to use global variables. what am i doing wrong here?

def func1(a):
global b
b = a * 2
return b
def func2():
global b
c = b * 2
print(c)

narrow kettle Jul 2, 2020, 12:39 PM

#

You didn’t declare a variable

wide shuttle Jul 2, 2020, 12:39 PM

#

So,

def foo():
    pass

and

name = "hello"

work very similarly

#

If you then move that same logic to a class definition, you see what happens:

#

class MyClass:
    name = "hello"
    
    def foo():
        pass

#

You're creating objects as usual (a str object and a function object); it's just that the names here are class attributes

#

So, MyClass.foo will be assigned to the function object in memory and MyClass.name to the str object

#

The function object is just a normal function object

#

That's why you could also do:

#

!e

def my_odd_method(self):
    print(self)


class MyClass:
    method = my_odd_method


obj = MyClass()
obj.method()

fallen slateBOT Jul 2, 2020, 12:42 PM

#

@wide shuttle :white_check_mark: Your eval job has completed with return code 0.

<__main__.MyClass object at 0x7fa03da3f9d0>

wide shuttle Jul 2, 2020, 12:42 PM

#

There's nothing special about the function objects you define within a class namespace

#

The "magic" of inserting the instance (for self) happens when you access the class attribute on the instance of the class

rigid tundra Jul 2, 2020, 12:48 PM

#

So, again humor me please. I would like to go back to what I said initially. I said "no variable scope in methods", wherein I meant that you can create a variable where ever you want inside of a method and it exists. As @flat gazelle pointed out, this becomes invalid when I created another method within a method which directly proves my statement incorrect. How can I tailor my statement to be correct? Would it be only that there is not scope within "blocks" as @spark magnet said?

flat gazelle Jul 2, 2020, 12:49 PM

#

ye, I would say blocks do not create scope. Also method != function in python

#

as per Ves

rigid tundra Jul 2, 2020, 12:49 PM

#

@wide shuttle Also thank you for the little lesson on objects

wide shuttle Jul 2, 2020, 12:50 PM

#

"methods" are just regular function objects, so local names will go out of scope

#

However, we typically mutate the object the method is "acting on"

#

Like self.attribute = something

languid dagger Jul 2, 2020, 12:51 PM

#

You need to use nonlocal same as with global for nested functions

rigid tundra Jul 2, 2020, 12:53 PM

#

I learned something today 🙂

spark magnet Jul 2, 2020, 12:54 PM

#

@rigid tundra i see, it was the ambiguity of "in" that tripped us up.

#

"There are no new scopes created within methods other than the method scope itself"

rigid tundra Jul 2, 2020, 12:57 PM

#

@spark magnet Yea, I thought that I had said in it in a correct way and I was confused when you guys said it was wrong, but I understand how I phrased it incorrectly

spark magnet Jul 2, 2020, 12:57 PM

#

it wasn't incorrect it turns out. it's just hard to be super-precise.

flat gazelle Jul 2, 2020, 12:58 PM

#

phrasing is hard, but you had the right idea, and that is what matters

rigid tundra Jul 2, 2020, 1:03 PM

#

Wait wait wait.... so even though it was ambiguous I'm technically right with my phrase? I thought that because of the ambiguity of the use of "in" that it was incorrect because you can declare another method inside of the method and still have scope, and the way that I phrased it I said "no variable scope in methods" is false with that example mentioned.

flat gazelle Jul 2, 2020, 1:04 PM

#

that is kind of the sole exception. But it is clear that the statement does not consider that as the claims it makes cannot be true in the case of nested methods

dry oar Jul 2, 2020, 1:05 PM

#

cant you add variables to input texts?

rigid tundra Jul 2, 2020, 1:06 PM

#

@flat gazelle Thank you for the clarification, my biggest fear is always looking like an idiot because I didn't get the proper diction or phrasing correctly 😉

flat gazelle Jul 2, 2020, 1:07 PM

#

if someone calls you dumb for a slightly incorrect statement, they are the dumb one. Now knowing something is not shameful

rigid tundra Jul 2, 2020, 1:12 PM

#

So unfortunately I was never able to take a course in python directly, I had many projects through courses especially in my last year that got me to pick up python, and I feel decent at programming in it. However, I definitely lack the understanding of the language complexities such as scope, and immediately before that loop indexing. Does anyone have any recommendations as to where I may be able to find a good overview of very language specific things that python has that other languages do not?

wide shuttle Jul 2, 2020, 1:16 PM

#

There are a couple of great videos on YouTube that could help you with getting familiar with some of the core mechanisms in Python

#

In fact, nedbat gave a couple of really good talks on PyCon

#

They explain things like how assignment works in Python (the relationship between names and values) and looping (that talk uses Python 2, but it's still great)

#

Ned Batchelder - Facts and Myths about Python names and values https://www.youtube.com/watch?v=_AEJHKGk9ns
Ned Batchelder - Loop like a native https://www.youtube.com/watch?v=EnSu9hHGq5o

#

There are also a lot of other great talks, by Raymond Hettinger (e.g., Beyond PEP-8 https://www.youtube.com/watch?v=wf-BqAjZb8M) and others

#

Other than that, there are great books like Fluent Python (the second edition will be released on Feb 9, 2021)

rigid tundra Jul 2, 2020, 1:21 PM

#

@wide shuttle Awesome! I will be taking a look at these. @wide shuttle @flat gazelle @spark magnet @sacred tinsel Thank you for your time

smoky torrent Jul 2, 2020, 1:35 PM

#

guys, i am learning python as my first coding language, and really have a hard time remembering all the
different commands and so on
any advice ? did you have this problem aswell?

flat gazelle Jul 2, 2020, 1:41 PM

#

I suggest just writing them down in one place for easy lookup. With practice, they stick

#

that is what I do when I am using a language I am not all that used to

#

generally, you want to google something python cheat sheet

spark magnet Jul 2, 2020, 1:45 PM

#

@smoky torrent btw, it's better not to start the same discussion in two channels at once

smoky torrent Jul 2, 2020, 1:45 PM

#

alright, wont do it again:)

unkempt rock Jul 2, 2020, 2:12 PM

#

how do i normalize number between 0-20

subtle pike Jul 2, 2020, 2:27 PM

#

>>> xs = [*range(200)]
>>> min_x = min(xs)
>>> max_x = max(xs)
>>> xs_norm = [20 * (x - min_x) / (max_x - min_x) for x in xs]
>>> xs_norm[:3]
[0.0, 0.10050251256281408, 0.20100502512562815]
>>> xs_norm[-3:]
[19.798994974874372, 19.899497487437184, 20.0]

@unkempt rock

#

that is a statistics question, not a python language related question

#

preferably, use the appropriate channel

daring siren Jul 2, 2020, 3:05 PM

#

Anyone aware of the speed of len()? Is it true that it's just O(1)?

wide shuttle Jul 2, 2020, 3:07 PM

#

There's no single time complexity for the len function, as it depends on how it's implemented for the type

#

For most built-in types, the len just gets read off of a field in the C struct, which does make it fast

daring siren Jul 2, 2020, 3:07 PM

#

Well, the most common implementation is Cpython, right?

wide shuttle Jul 2, 2020, 3:07 PM

#

but, since you can implement support for len using the __len__ dunder in your own user-defined classes, it could be anything

brave badger Jul 2, 2020, 3:08 PM

#

From what I've read here it's supposedly O(1) for lists https://wiki.python.org/moin/TimeComplexity

daring siren Jul 2, 2020, 3:08 PM

#

Well I'll need to run it on strings, so I'm guessing I'm fine

wide shuttle Jul 2, 2020, 3:08 PM

#

I think that page only lists it for list, @brave badger

brave badger Jul 2, 2020, 3:08 PM

#

Yep

wide shuttle Jul 2, 2020, 3:09 PM

#

For strings, it's the same

#

It just reads it directly from a field in the C struct

peak spoke Jul 2, 2020, 3:09 PM

#

strings should keep that info since they're constant size

wide shuttle Jul 2, 2020, 3:10 PM

#

but, for custom user-defined classes, you could write your own crappy implementation

peak spoke Jul 2, 2020, 3:10 PM

#

I believe most, if not all, builtin sequences should keep it around since it's a lot cheaper to change on changes than counting when accessed

wide shuttle Jul 2, 2020, 3:11 PM

#

They should probably do that anyway, to keep track of the memory allocation

#

You could always cheat, of course

from collections import UserList


class MyList(UserList):
    def __len__(self):
        count = 0
        for element in self:
            count += 1
        return count

daring siren Jul 2, 2020, 3:19 PM

#

It's fine, I won't do any of that

#

Thanks guys!

flat gazelle Jul 2, 2020, 3:30 PM

#

linked list have O(n) length query. And are one of the few data structures where n can actually be infinite

silent spear Jul 2, 2020, 3:54 PM

#

Can someone explain to me what objects are

#

I already understand what classes are but I still don't understand objects are

visual shadow Jul 2, 2020, 3:55 PM

#

Objects are the "realisation" of classes

#

If "human" is a class, then "you" are one object of the human class.

#

A class is like a blueprint. An object is like an actual item made from that blueprint.

silent spear Jul 2, 2020, 3:56 PM

#

Oh ok

#

Thx

wide shuttle Jul 2, 2020, 4:14 PM

#

@livid geyser Could you show me an example of what you mean?

#

Because it would work if you do this:

#

!e

def my_strange_method(self):
    print(self)


class Foo:
    method = my_strange_method

f = Foo()
f.method()

fallen slateBOT Jul 2, 2020, 4:15 PM

#

@wide shuttle :white_check_mark: Your eval job has completed with return code 0.

<__main__.Foo object at 0x7fba609bf9d0>

livid geyser Jul 2, 2020, 4:15 PM

#

If I

class Test:
  pass
def myfunc(self, *args):
  pass
Test.myfunc = myfunc```
Test.myfunc doesn't get self

#

Wait what

#

I swear I've literally done that and it doesn't bind

#

Wait no it's bound in the class

wide shuttle Jul 2, 2020, 4:16 PM

#

Right, when you access the class attribute on the class object directly, you get the function object back as-is

livid geyser Jul 2, 2020, 4:16 PM

#

!e

class Test:
  pass
def myfunc(self, *args):
  print(self)
Test.myfunc = myfunc
Test().myfunc()

fallen slateBOT Jul 2, 2020, 4:16 PM

#

You are not allowed to use that command here. Please use the #bot-commands channel instead.

wide shuttle Jul 2, 2020, 4:16 PM

#

but that holds for "normal" methods as well

livid geyser Jul 2, 2020, 4:16 PM

#

oh

wide shuttle Jul 2, 2020, 4:16 PM

#

!e

class Test:
  pass
def myfunc(self, *args):
  print(self)
Test.myfunc = myfunc
Test().myfunc()

fallen slateBOT Jul 2, 2020, 4:16 PM

#

@wide shuttle :white_check_mark: Your eval job has completed with return code 0.

<__main__.Test object at 0x7ff72d6e69d0>

wide shuttle Jul 2, 2020, 4:16 PM

#

That works fine

livid geyser Jul 2, 2020, 4:16 PM

#

Wait what

wide shuttle Jul 2, 2020, 4:16 PM

#

However, if you were to do Test.myfunc(), it wouldn't work

livid geyser Jul 2, 2020, 4:16 PM

#

I have literally done that in my code before and it behaved weirdly

#

I'm so confused lol

wide shuttle Jul 2, 2020, 4:17 PM

#

!e

class Test:
    def name(self):
        pass

print(Test.name)

fallen slateBOT Jul 2, 2020, 4:17 PM

#

@wide shuttle :white_check_mark: Your eval job has completed with return code 0.

<function Test.name at 0x7f462243de50>

wide shuttle Jul 2, 2020, 4:17 PM

#

If you access the class attribute on the class object (instead of on an instance), you get the function itself back

livid geyser Jul 2, 2020, 4:17 PM

#

Did that get changed at some point or am I going mad lol

wide shuttle Jul 2, 2020, 4:17 PM

#

It won't "bind" an instance, since there is no instance to bind

#

However, if you access the class attribute on an instance, you do get the binding

#

!e

class Test:
    def name(self):
        pass

t = Test()
print(t.name)

fallen slateBOT Jul 2, 2020, 4:18 PM

#

@wide shuttle :white_check_mark: Your eval job has completed with return code 0.

<bound method Test.name of <__main__.Test object at 0x7f11e95f19d0>>

wide shuttle Jul 2, 2020, 4:18 PM

#

As you can see, we're no longer getting a function object back, but a bound method

livid geyser Jul 2, 2020, 4:18 PM

#

Yeah I know about that much

#

Maybe when I did it I messed up and bound it to the instance instead of the class

wide shuttle Jul 2, 2020, 4:18 PM

#

Did you assign an instance attribute to the function object?

livid geyser Jul 2, 2020, 4:18 PM

#

(N.B. by bound I mean set attr)

#

I probably did tbth

#

My bad lmao sorry for the wasted time

#

Hope your dinner was nice lol

wide shuttle Jul 2, 2020, 4:19 PM

#

Still busy cooking

livid geyser Jul 2, 2020, 4:19 PM

#

Oh ok lol

wide shuttle Jul 2, 2020, 4:19 PM

#

although I don't really have to do anything atm

crimson dragon Jul 2, 2020, 6:08 PM

#

Can I export python file with "pygal" package to browser without html and etc

unkempt rock Jul 2, 2020, 7:07 PM

#

i cannot use pyaudio on my pc its showing error download microsoft visual studio but i have downloaded new version

radiant fulcrum Jul 2, 2020, 7:23 PM

#

This channel isnt really for help, 2) its not VS you need its c++ build tools if you read the error carefully

unkempt rock Jul 2, 2020, 7:32 PM

#

Oooh c++ stuff 🙂

pure seal Jul 2, 2020, 7:44 PM

#

Hello

cloud crypt Jul 2, 2020, 7:49 PM

#

Damn

#

memoryview is actually hella cool