python equivalent of functools 'partial' for a class / constructor

Question

I want to create a class that behaves like collections.defaultdict, without having the usage code specify the factory. EG: instead of

class Config(collectio         


        

Answer 1

I don't think there's a standard method to do it, but if you need it often, you can just put together your own small function:

import functools
import collections


def partialclass(cls, *args, **kwds):

    class NewCls(cls):
        __init__ = functools.partialmethod(cls.__init__, *args, **kwds)

    return NewCls


if __name__ == '__main__':
    Config = partialclass(collections.defaultdict, list)
    assert isinstance(Config(), Config)