What is the difference between using list and List when defining for example the argument of a function in python3? For example, what is the difference between
def do_something(vars: list):
and
def do_something(vars: List):
The documentation says:
class typing.List(list, MutableSequence[T])
Generic version of list. Useful for annotating return types.
but I'm not entirely sure what the above means.
I have similar questions for: dict vs Dict, set vs Set, etc.
Not all lists are the same from a typing perspective. The program
def f(some_list: list):
return [i+2 for i in some_list]
f(['a', 'b', 'c'])
won't fail a static type checker, even though it won't run. By contrast, you can specify the contents of the list using the abstract types from typing
def f(some_list: List[int]) -> List[int]:
return [i+2 for i in some_list]
f(['a', 'b', 'c'])
will fail, as it should.
list[int] works now.
list instead of List as typing annotation in python 3.8 and older will cause Typeerror: type object is not subscriptable 
List, Dict, etc (with a capital letter) were deprecated since Python 3.9 e.g. Deprecated since version 3.9: builtins.tuple now supports []. See PEP 585 and Generic Alias Type. You can use just list instead. The old types are left for backwards compatibility if you need to use them.