Published: 12 November 2020, 18:00
PEP-560 (landed in Python 3.7) introduced a new magic method __class_getitem__
. it is the same as __getitem__
but for not instancinated class. The main motivation is easier type annotation support for generic collections like List[int]
or Type[Dict[str, int]]
:
class MyList:
def __getitem__(self, index):
return index + 1
def __class_getitem__(cls, item):
return f"{cls.__name__}[{item.__name__}]"
MyList()[1]
# 2
MyList[int]
# 'MyList[int]'