crazyguitar / pysheeet

Python Cheat Sheet

Introduction

Pysheeet was created with intention of collecting python code snippets for reducing coding hours and making life easier and faster. Any contributions are welcome. Please feel free to fork and send a pull request to this project.

What’s New In Python 3

This part only provides a quick glance at some important features in Python 3. If you're interested in all of the most important features, please read the official document, What’s New in Python.

• New in Python3

Cheat Sheet

• Code Style
• From Scratch
• Future
• Unicode
• List
• Set
• Dictionary
• Heap
• Function
• Class
• Generator
• Typing
• Time
• File
• Operating System

Advanced Cheat Sheet

• Regular expression
• Socket
• Asyncio
• Concurrency
• Sqlalchemy
• Security
• SSH
• Tests
• C Extensions

Appendix

• Why does Decorator Need @wraps
• A Hitchhikers Guide to Asynchronous Programming
• Asyncio behind the Scenes
• PEP 572 and the walrus operator
• Python Interpreter in GNU Debugger

PDF Version

pdf

How to run the server

$ virtualenv venv
$ . venv/bin/activate
$ pip install -r requirements.txt
$ make
$ python app.py

# URL: localhost:5000

pysheeet's Issues

Some suggestions

suggestions from feedback

Translate to portuguese

Hi!!

I'm thinking of proposing a portuguese translate.

But, I need your permission.

A better try..except... implementation in C

https://github.com/drh/cii/blob/master/include/except.h
https://github.com/drh/cii/blob/master/src/except.c

c o

mismatch result in page 51

>>> def subgen():
...     try:
...         yield 9527
...      except ValueError:
...          print("get value error")
...
>>> def delegating_gen():
...     yield from subgen()
...
>>> g = delegating_gen()
>>> try:
...     next(g)
...     g.throw(ValueError)
... except StopIteration:
...     print("gen stop")
...
9527
get value error
gen stop

in my desktop Python 3.6.2 Anaconda, I run the code above in IPython, but the output dose not contain the first line '9527'.

国-酩酊大醉 ***★......ᄒ笔7卤

Add example for variable names with multiple words

Regarding https://www.pythonsheets.com/notes/python-basic.html#python-naming-styles.

An example for variable names with compound words would be nice.
For example. Should a method local variable be called userName or user_name?

Dependabot couldn't authenticate with https://pypi.python.org/simple/

Dependabot couldn't authenticate with https://pypi.python.org/simple/.

You can provide authentication details in your Dependabot dashboard by clicking into the account menu (in the top right) and selecting 'Config variables'.

View the update logs.

Python3 integer division

https://www.python.org/dev/peps/pep-0238/

Feature Request - Floating TOC

It would be great to have a floating TOC navigation for long cheatsheets

Weird variable name

• Line from app_test.py:

for h in htmls:
    u = "notes/" + h
    resp = static_proxy(u)

• What is u and h?
• From reading app.py i realized that variable u is path.
• Maybe, you need to give variables meaningful names?

Cheatsheet for string manipulations

Is someone will attend this issue I'm newbie here i just want to learn and someone will mentor me about programming it will much appreciated

/%0在@

sqlalchemy cheat sheet: Reflect=True is depreciated. Change to use the reflect() method

Reflect=True still works but is depreciated.

Not all parts of the cheat sheet need to be changed, but a lot of it still uses reflect=true.

Iterator 404

Hi
The iterator page is not there, is it deleted or being updated ?

Thanks

Appendix: Yet Another Introduction to Asyncio

missing explanation.

• flow graph
• explanation

Migrate alll codes to just python 3

Can we migrate all code snippets in this repo to python 3 to not confuse the new user to use the deprecated python 2.x. Its just a suggestion as of now.

pep-0328 - guido-s-decision

Python3 changes that relative imports will use leading a dot.

reference:

• Guido's Decision
• stack overflow

socket cheat sheet: AF_INET6 missing

As someone who struggles with finding the right combination of AI_V4MAPPED because he doesn't want to implement things twice for IPv4 and IPv6, I find the lack of AF_INET6 examples disturbing.

IPv4 might not be dead yet, but is on a good way to its sunsetting phase.

Please consider adding IPv6 examples, or even making IPv6 (possibly with V6ONLY=0) the default.

New version of fundamental cheat sheets

Make brief explanations become part of cheat sheets.

• Style
• From Scratch
• Future
• Unicode
• List
• Set
• Dictionary
• Function
• Classes and Objects
• Generator
• Typing
• Files and I/O

make the glossary a bit clearer

in two cases you do g = ... while in once case you want to explain

calling the generator function returns a generator

and in the other you mean

(x for x in seq) is a generator expression evaluating directly to a generator.

i think you should make this clear.

fib error

the function fib has error,others is right

There doesn't seem to be any coverage of 'map()'

At least, not when I search for it in the search box on the Table of Contents.

Perhaps this was intentional?

Thanks for all the great work on this.

Default to Python 3 compatibility

Thank you for maintaining this great resource!

With Python 2 End of Life planned for about 19 months from now, it should be possible to run any snippet found on pysheets under the latest version of Python (3.6.5 today) unmodified. For example, all occurrences of print should be functions instead of statements. This is not to say that the snippets should not run under Python 2, but that the priority should be Python 3 compatibility.

Dictionary changes

It might be worth adding a section on how the handling of dictionaries has changed between 2 and 3 in the New in Python3 cheatsheet

Building a PDF via Sphinx fails

There seem to be a lot of unicode issues. I have no clue how to fix them, but having a PDF would be neat.

git clone https://github.com/crazyguitar/pysheeet
cd pysheeet/docs
make latexpdf

! Package inputenc Error: Unicode char 中 (U+4E2D)
(inputenc)                not set up for use with LaTeX.

See the inputenc package documentation for explanation.
Type  H <return>  for immediate help.
 ...

l.1677 ...G{l+s+s1}{中文}\PYG{l+s+s1}{\PYGZsq{}}

mapper() func is deprectiated

Per the SQLAlchemy docs, the mapper() function is depreciated. The docs suggest using registry.map_imperatively() to get the same functionality used in pysheeet.

@crazyguitar I'd be happy to open a PR & update the syntax - just be patient with me, as I'm still learning :)

Appendix: Why does Decorator Need @wraps

missing explanation.

P. List

In Remove <>

In the Python 3 part is

a != "Python2"
True
The result should be False or the check should be a != "Python3"

K.

Review advanced cheat sheets

• Regular Expression
• Socket
• Asyncio
• Concurrency
• SQLAlchemy
• Security
• Boto3
• Test
• C Extensions

Lots of issues

https://www.reddit.com/r/Python/comments/6utwyn/a_python_cheat_sheet_about_security/dlvo6n2/

DateTime Column is not coded properly

Hi

This page has the following code for the ORM

https://www.pythonsheets.com/notes/python-sqlalchemy.html

class TestTable(Base): __tablename__ = 'Test Table' id = Column(Integer, primary_key=True) key = Column(String, nullable=False) val = Column(String) date = Column(DateTime, default=datetime.utcnow)

The proper way to code the DateTime column is

class TestTable(Base): __tablename__ = 'Test Table' id = Column(Integer, primary_key=True) key = Column(String, nullable=False) val = Column(String) date = Column(DateTime(), default=datetime.utcnow)
If you use the code from your example and have two DateTime columns coded this way then SQLalchemy will raise this error on the second column. sqlalchemy.exc.ArgumentError: Column must be constructed with a non-blank name or assign a non-blank .name before adding to a Table.

Translation for korean

How awesome is this!

I wanna spread these great notes to korean, So I would like to translate this into korean after fork.

Are there some rules for translation contributing? And, when I’m done, can I link the korean repository to this README later?

Thank you!

Add boto3

• S3
• DynamoDB
• SQS
• Lambda

New in Python 3: delegate() ignores its argument

In the example of Generator delegation, the delegate function ignores its argument and calls fib() with a hard-coded value of 10. This is probably unintended.

NameError: abort()

flake8 testing of https://github.com/crazyguitar/pysheeet on Python 2.7.13

$ flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

./app.py:42:21: F821 undefined name 'abort'
    if key is None: abort(404)
                    ^

What license is this under?

A very nice piece of work. Is this licensed under creative commons?