gto76 / python-cheatsheet Goto Github PK

I love this cheat sheet!
It would be great to add some points about how to make production-grade code, such as:

• virtual environment (e.g., with virtualenvwrapper)
• test (unittest, pytest, mock, tox)
• packaging and installation (setuptools, pip, ...)

Some points about how "import" works would be great too (one of the most used yet not understood feature in Python)
I realize that those are quite broad topics (especially the last one), but that would sure be very helpful

Add a LICENSE.txt file in the root of the repo, with an appropriate license (my vote would be for MIT, BSD, Apache, or CC-BY)

Cheatsheet

• MemoryView
• Pathlib
• Asyncio
• Datetime
• Logging
• Dataclass

Page

• Static page (Automatic generation of index.html from README.md at commit)
• Better mobile experience (Help needed)
• Back to top button (Help needed)

Hi,

What was the design choice around using strong emphasis (double asterisks) for most non-code text?

Would be nice to have nice printable PDF for the wall hangers enthusiasts 🥇

Code For plotly can be changed to make it look more clear in dark background.

Add a directory on top of the Readme to skip to desired stuff

Hello,
I think adding a licence file would be useful as the actual licence of the project is a bit ambiguous (it is by default not possible legally to use any of the code in the cheatsheet).
Is it on purpose ?

Thank you

I learned that there are two ways to encode and decode bytes. One has been included:

<bytes> = <str>.encode(encoding='utf-8')
<str>   = <bytes>.decode('utf-8') 

the other is

<bytes> = bytes(<str>,encoding='utf-8')
<str> = str(<bytes>,encoding='utf-8')

Just to remind:-D. May be you just choose the one you prefer~

Thanks for the Cheat Sheet

thank you

Firstly, nice doc.

For exceptions, having a comment on which is executed for what failures would be good for else and finally

Navigating the HTML version of this cheat sheet would be easier if there was a floating table of contents.

import itertools
nested_list1 = ["s", "r", [32, [32], 3]]
flattened_list1 = list(itertools.chain.from_iterable(nested_list1))
print(flattened_list1)
nested_list2 = [1, [1, 1, 3, [224, 4], []], [], [2, [23]]]
flattened_list2 = list(itertools.chain.from_iterable(nested_list2))
print(flattened_list2)
# RESULT
# ['s', 'r', 32, [32], 3] (flattened_list) <-- not completely flat
# TypeError: 'int' object is not iterable (flattened_list2)  <-- doesnt work at all

I suggest:

from copy import deepcopy
def flatten(nested):
    """Flatten an arbitrarily nested list."""
    nested = deepcopy(nested)
    flat = []
    while nested:
        sublist = nested.pop(0)
        if isinstance(sublist, list):
            nested = sublist + nested
        else:
            flat.append(sublist)
    return flat
list1 = flatten(nested_list1)
list2 = flatten(nested_list2)

print(list1)
print(list2)
# RESULT
# ['s', 'r', 32, 32, 3] (list1)
# [1, 1, 1, 3, 224, 4, 2, 23] (list2)

In python 3.8 there is a more elegant way to calculate the product of the elements.

Instead of
product_of_elems = functools.reduce(lambda out, el: out * el, <collection>)
it can be done like this
product_of_elems = math.prod(<collection>)

Full python code cheats

The codes are superb!

The definition of any(collection) says "False if empty", but that's not the whole story.

any( [ False ] ) is False even though the argument is not empty.

Клалаьа

from datetime import datetime, strptime
now = datetime.now()
now.month                     # 3
now.strftime('%Y%m%d')        # '20180315'
now.strftime('%Y%m%d%H%M%S')  # '20180315002834'
<datetime> = strptime('2015-05-12 00:39', '%Y-%m-%d %H:%M')

The first line has a typo and should be from datetime import datetime, strftime.
But you can't import strftime from the root module.

datetime.datetime.now() returns a datetime object, and those can be called with strftime I.E.

from datetime import datetime
datetime.now().strftime('%b')
# --> Feb

Simply the first line just needs the last word deleted off. Don't forget the typo in the last line either ;)

I'd take this opportunity to mention a few cool tricks about from datetime import date but I'm at work right now. If I get a chance later I may open a pull request.

RomaMolora

I've seen tons of "cheat sheets" but this one is different. I'm still trying to figure how to to make it part of my coding environment. I may add some tools around it, like I did a tool called "How Do I" that queries Stack Overflow. I made a GUI. I may make a GUI for this too or something that allows easy access from PyCharm so I never leave my coding environment.

I dunno yet exactly how to integrate this amazing documentation, but, I do know it's a true gem of a find.

I wonder if you’ve considered the operator convenience functions itemgetter and attrgetter for list sorting:

https://docs.python.org/3.7/howto/sorting.html#operator-module-functions

I find them cleaner than using lambda functions, and the documentation claims that they also have better performance.

No issue at all. I just wanted to thank you for making your cheatsheet available. Really comprehensive and helpful – very much appreciated! 👍

Python

Read thru the source, and in the process markdown linted and reformated the source for readability.
I don't know how/if I can upload the git commit, so I attached source file here.
Feel free to use any of my suggested changes to the source.
Thanks
README.md

In this section:

out = [i+j for i in range(10) for j in range(10)]

Is the same as:

out = []
for i in range(10):
    for j in range(10):
        out.append(i+j)

The loop variables i and j should be swapped in either the first or the second part. Maybe one of the 10s could even be changed into another value to make it clearer? For instance:

out = [i+j for j in range(5) for i in range(10)]

Is the same as:

out = []
for i in range(10):
    for j in range(5):
        out.append(i+j)

The basic flow control syntax for if, else, elif, for, and while do not seem to be included.

Thank 👍