Published: 07 July 2020, 18:00
Python 3.6 introduced a few hooks to simplify things that could be done before only with metaclasses. Thanks to PEP-487. The most useful such hook is __init_subclass__
. It is called on subclass creation and accepts the class and keyword arguments passed next to base classes. Let’s see an example:
speakers = {}
class Speaker:
# `name` is a custom argument
def __init_subclass__(cls, name=None):
if name is None:
name = cls.__name__
speakers[name] = cls
class Guido(Speaker): pass
class Beazley(Speaker, name='David Beazley'): pass
speakers
# {'Guido': __main__.Guido, 'David Beazley': __main__.Beazley}