🔒 'None' data type

[trim pilot]

From the book, it confuses me...can someone help me understand

1. What none type is?
2. why is it used?
3. where can i use?

[honest mango]

@trim pilot

Python help channel opened

Remember to:

• Ask your Python question, not if you can ask or if there's an expert who can help.
• Show a code sample as text (rather than a screenshot) and the error message, if you've got one.
• Explain what you expect to happen and what actually happens.

:warning: Do not pip install anything that isn't related to your question, especially if asked to over DMs.

Closes after a period of inactivity, or when you send !close.

[zenith shard]

1. NoneType

!d types.NoneType

[honest mango]

types.NoneType

types.NoneType```
The type of [`None`](https://docs.python.org/3/library/constants.html#None).

Added in version 3\.10\.

[zenith shard]

2. for whatever reason you liked but usually when you don't have stuff to return

e.g. Your function might try to obtain a record from database, and you could return None when no record is found (or you could raise an exception which doesn't need None)

it can also be used as default value for function parameter

3. everywhere but ^

[bleak plover]

It's the default return value of functions, because functions are always required to return a python object of some kind

[bleak plover]

Can you say which page of which book?

[trim pilot]

return

simply give None?

[zenith shard]

yes

[bleak plover]

!e

return

[honest mango]

:x: Your 3.12 eval job has completed with return code 1.

001 |   File "/home/main.py", line 1
002 |     return
003 |     ^^^^^^
004 | SyntaxError: 'return' outside function

[zenith shard]

!e

def f1(): return
print(f1())

[honest mango]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

None

[zenith shard]

have to use it in a function :)

and there are something call implicit return

[trim pilot]

wait

i am sending

[zenith shard]

!e

def f1(): ... # Do literally nothing
print(f1())

[honest mango]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

None

[trim pilot]

ok got it

can we use at any other place in the code

[zenith shard]

returnnope, it have to be in a function

Noneyes, everywhere

just

!e

None

[honest mango]

:warning: Your 3.12 eval job has completed with return code 0.

[No output]

[zenith shard]

see, you used it :)

[trim pilot]

here?

[zenith shard]

?

[bleak plover]

Try it out

Use a code block and !e

!code

[honest mango]

Formatting code on Discord

Here's how to format Python code on Discord:

```py
print('Hello world!')
```

These are backticks, not quotes. Check this out if you can't find the backtick key.

For long code samples, you can use our pastebin.

[tribal gate]

Yes, you can assign it to a variable just like any other value. It's usually used to say "no value was given"

[trim pilot]

new = input('Enter a number')
print(new)```

it is printing none if i enter none..
i doubt that there should be no value printed by it

[bleak plover]

That's the str 'None'

Which looks like None when you print it

!e

print('None')
print(None)

[trim pilot]

👍

[honest mango]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | None
002 | None

[trim pilot]

both?

[bleak plover]

They look the same if you print them, something to watch out for

[trim pilot]

ok

[bleak plover]

This is to do with the __repr__ and __str__ methods

[trim pilot]

what are these?

nvm lets code

[bleak plover]

A bit complicated, but important to get right if you use them:

https://docs.python.org/3/reference/datamodel.html#object.__repr__
https://docs.python.org/3/reference/datamodel.html#object.__str__

[trim pilot]

not to learn this now

can you give me more examples

[bleak plover]

I think this is the most recent time I've used None: https://github.com/agronholm/anyio/commit/3a62738be0ba8d7934bd447e3833d644d414d49a#diff-bca1f1fd66614ba723b3440cc1656412e65106e3130c5ff68cbae1d15d9bf08bR189

[trim pilot]

what is this code for

github is what i am still learning to operate

i connected the github with vs code..
but i dont use it much..
it was so hectic to make it work

[tribal gate]

__str__ means "this is how you convert to a string", so str(None) == "None". __repr__ means "this is how I want something to be represented". They both give you a string, but they have a difference in meaning. I don't think it's important for you at this stage.

[rare heron]

Wow. This much text on None. None represents lack of value. For example a function that doesn't return anything in fact still returns None. Some other other languages might have null or nullptr or something else too, but Python has None.

[bleak plover]

This code is to check if an address is a domain name or an IP address. It tries to parse the address as a IP address and if it fails it assigns None instead. The code then processes the IP address or the None object differently

This is done because getaddrinfo is slow and expensive, and we want to skip it for IP addresses where it's redundant work

So it's using None here to represent an error case

[honest mango]

Python help channel closed

This help channel has been closed and it's no longer possible to send messages here. If your question wasn't answered, feel free to create a new post in #1035199133436354600. To maximize your chances of getting a response, check out this guide on asking good questions.