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[worthy summit]

def find_needle(haystack):
    for i in range(len(haystack)):
        if haystack[i] == "needle":
            return f"found the needle at position {i}"```
would this be the ideal solution? i feel like it could be a lot better.

[median basalt]

@worthy summit

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[terse trail]

You'd need to show the full question.
I'd expect such a function to just return i.

[worthy summit]

list of str
find "needle" in haystack
return the str "found the needle at position {n}"
where n is the index

[terse trail]

Oh, then it looks ok

[icy escarp]

that would be correct, this is actually a very good illustration of where hashing becomes relevant though

[worthy summit]

oh, really?

[terse trail]

not in a list 🙂

[worthy summit]

what is hashing?

[icy escarp]

hashing is what dictionaries use instead of indices

[inland kayak]

see the enumerate function

[worthy summit]

!d enumerate

[median basalt]

enumerate

enumerate(iterable, start=0)```
Return an enumerate object. *iterable* must be a sequence, an [iterator](https://docs.python.org/3/glossary.html#term-iterator), or some other object which supports iteration. The [`__next__()`](https://docs.python.org/3/library/stdtypes.html#iterator.__next__) method of the iterator returned by `enumerate()` returns a tuple containing a count (from *start* which defaults to 0) and the values obtained from iterating over *iterable*...

[terse trail]

Hashing is how dicts work.
You store values associated with keys.
To make lookup fast you distrubute the keys in a list, with the position of the key determined by a "hash" function. That way you can go to the specific list position directly from the key instead of searching linearly as your code does.

There are details, but that is the core.

[worthy summit]

oh

[icy escarp]

if you were trying to find a literal needle in a haystack, hashed lookup would be the equivalent of telling you exactly where it's located

[worthy summit]

interesting

[icy escarp]

there is also the index() function, which will return the same figure as your function

!d index

[median basalt]

index

A numeric value that represents the position of an element in a sequence.

In Python, indexing starts at zero. For example, things[0] names the first element of things; things[1] names the second one.

In some contexts, Python allows negative indexes for counting from the end of a sequence, and indexing using slices...

[terse trail]

but there's a cost to making the hash table in the first place, of course

[worthy summit]

im trying to use enumerate

[icy escarp]

forewarning though, normally when beginners are attempting to retrieve the index it's a misguided use of lists. The index is something you'd normally want to have readily available.

[worthy summit]

how do i return the enumerate object into something human readable?

[icy escarp]

list() works I think, or zip map dict()

[worthy summit]

oh nvm, i found out list works

[worthy summit]

ty

oh, enumerate is cool too

!e```py
def find_needle(haystack):
hay = dict(enumerate(haystack))
for key, value in hay.items():
if value == "needle":
return f"found the needle at {key}"

print(find_needle(["short", "fire", "needle"]))

[median basalt]

:white_check_mark: Your 3.14 eval job has completed with return code 0.

found the needle at 2

[worthy summit]

i feel like this could be a lot better too

the for loop was better

def find_needle(haystack):
    return f'found the needle at position {haystack.index("needle")}'```

OH SO THATS HOW IT WORKS

[inland kayak]

why are you using a dict here?

[worthy summit]

idk, i really just wanted a way to use the enumerate object

[inland kayak]

!enumerate

[median basalt]

The `enumerate` function

Ever find yourself in need of the current iteration number of your for loop? You should use enumerate! Using enumerate, you can turn code that looks like this:

index = 0
for item in my_list:
    print(f"{index}: {item}")
    index += 1

into beautiful, pythonic code:

for index, item in enumerate(my_list):
    print(f"{index}: {item}")

For more information, check out the official docs, or PEP 279.

[worthy summit]

oh

[median basalt]

Python help channel closed for inactivity

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