Class decorator that overrides default kwargs.

default_args_class_decorator.py

from functools import wraps


def defaults(method='__init__', **default_args):
    """Class decorator.  Overrides method default arguments."""

    def decorate(cls):
        func = getattr(cls, method)

        @wraps(func)
        def wrapper(self, *args, **kwargs):
            default_args.update(kwargs)
            return func(self, *args, **default_args)

        setattr(cls, method, wrapper)
        return cls

    return decorate

Overrides defaults without polluting the class namespace.
Defaults can be overridden again at runtime.

For example:

class FooBase(object):
    def __init__(self, a=1):
        self.a = a


@defaults(a=2)
class Foo(FooBase):
    pass


f = Foo()
assert f.a == 2  # Pass
g = Foo(a=3)
assert g.a == 3  # Pass

Class Foo is equivalent to:

class Foo(FooBase):
    def __init__(self, **kwargs):
        default_args = dict(a=2)
        default_args.update(kwargs)
        super(Foo, self).__init__(**default_args)

More examples:

• Note: It defaults to overriding __init__. But use the method keyword to override any method defaults.
• Note: The decorator is stackable and decorated objects are subclass friendly.

@defaults(a=4, b=6)
@defaults(method='add', a=3, b=5)
class Bar(object):
    def __init__(self, a=1, b=2):
        self.a = a
        self.b = b
        print(self.a)
        print(self.b)
        self.add()

    def add(self, a=7, b=9):
        print('a', a)
        print('b', b)


b = Bar()
# print 4
# print 6
# print a 3
# print b 5

b.add(a=35)
# print a 35
# print b 5