Python Generic List

list.py

'''
C# like generic lists for python!
Description
  A cool trick that uses a singleton variable called "List" which is an instance of a "hidden" class _GenericList
  this class defines a __getitem__ method that returns a type object that internally stores the type given by the getter
  because it is a type object you can instanstiate in python using curly braces, hence behaving exactly like a normal class
  
  The class _GenericList also returns a regular list instance if no type were provided, this is done by defining the __call__ method
  
Usage:
  Import this module
    Make sure the variable List is set before using it
  Create a generic list by putting the desired type inside square brackets
   ``` 
    l = List[int](1,2,3)
   ```
  Append/Insert methods work as well
   ``` 
    l = List[str]()
    l.append('Hello')
   ```
   Attempts of adding an element of a different type will result in an Error
   ``` 
    l = List[int]()
    l.append('Hello')  # AssertionError
   ```
 Downsides:
    Type checking occurs at runtime which makes the process slower
'''

class _GenericList:
	def __getitem__(self, _type):
		assert type(_type) is type
		class ListWrapper(list):
			def __init__(self, *args):
				assert all(isinstance(item, _type) for item in args)
				super().__init__(args)
			
			def append(self, __object) -> None:
				assert isinstance(__object, _type)
				super().append(__object)
			def insert(self, __index, __object):
				assert isinstance(__object, _type)
				super().insert(__index, __object)
			def __add__(self, _value):
				assert isinstance(_value, type(self))
				super().__add__(_value)
			
			def __setitem__(self, __key, __value):
				if type(__key) is int:
					assert isinstance(__value, _type)
				elif type(__key) is slice:
					assert isinstance(__value, type(self)) \
						or all(isinstance(value, _type) for value in __value)
				else: raise IndexError(type(__key).__name__)
				super().__setitem__(__key, __value)

			def __repr__(self) -> str:
				return f'List({_type.__name__})' + super().__repr__()
		return ListWrapper
	def __call__(self, *args):
		return list(args)
	def __repr__(self):
			return 'List'
List = _GenericList()

You may think this solution is not elegant, but is exactly how the typing library works tho