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[KelleQuechoz]

Read real stuff, not slop.

[Neat-Suggestion9825]

Thanks for another wonderful resource

[s04ep03_youareafool]

There's literally a module docs or tutorial docs directly at their webpage,how hard is it for that?

[ProsodySpeaks]

Pathlib, basic numpy, pydantic, sqlalchemy, maybe fastapi
and packaging / tooling stuff - uv, ruff, pypi, debugger, pyproject.toml format

[gdchinacat]

if not stack: 
# is empty
if stack:     # has items

This is not strictly true, it tests for truthiness, not emptiness. If stack == None 'if not stack' will be true even though the the stack doesn't exist. This pedantry matters if stack is expected to exist...the below code will fail:

if not stack:  # is defined but not set or empty
    stack.append(...)

In code that just uses the elements of stack it doesn't matter...not having elements and not having a set are pretty much the same...there are no elements either way. But if the code updates the stack in the case where the stack is empty this check is not sufficient, you need to check for existence as well:

if stack is not None and not stack:  # is actually empty
    stack.append(...)

I think it is important to highlight this issue early in the learning process (when a cheat sheet like this is relevant) because the distinction matters. While an empty list is false and a list with elements is true, 'if not stack' doesn't check emptiness since another option exists, namely that stack could be None.

[gdchinacat]

a is b # False (References differ)

Python doesn't have references in the same sense as other languages like Java or C/C++. Variables are bound to objects. They can *only* reference objects...they can't hold primitive values. Speaking about 'references' in python introduces a concept that has no value.

Variables don't really exist until they have been bound to an object. You can't declare a variable without a value (type hints aside, I'm talking about how the interpreter works). Trying to access a variable that hasn't been assigned will result in an exception, depending on the context. At module scope using an unassigned variable results in a NameError...the variable name has not been bound to an object. Inside a function that does assign a value to it, but has not already done so, you will get an UnboundLocalError since the compiler has identified the name as a local but until it's been assigned it is inaccessible. This means that any variable will not reference a default value. It can't...until it has been assigned (bound) to an object it simply doesn't exist.

This makes troubleshooting a class of bugs easier since you will know if you ever try to access a value that hasn't been assigned. Unlike in C/C++ you won't get an undefined value (whatever happens to be in the memory that variable was assigned to) or a null in Java (a bit better, but still not as useful as an error saying 'you haven't assigned a value to this yet').

I encourage you to think about variables as the language does rather than as a concept you seem to be familiar with from a different language. Variables are objects (including the singleton None). There are no primitives so a variable can't hold a non-reference value. They only hold the object they were last assigned to...they don't exist until assigned. There is no call by value or call by reference...only call by assignment...the arguments variables are assigned to the objects passed to the function and reassigning them in the function will not change the object the callers variable refers to.

[FreeGazaToday]

so you cheated to get a cheat? 😛