def __init__(self, **inputs):
    if 'a' not in inputs:
        inputs['a'] = 1
if 'b' not in inputs:
    inputs['b'] = 2
self.bar(**inputs)

def __init__(self, **inputs):
    args = {'a': 1, 'b': 2}
args.update(inputs)
self.bar(**args)
Pack function arguments into a dictionary - opposite to **kwargs