在__init__中打开** kwargs

Question

I've stripped down my problem into the simplest possible code:

class Billy:
    def __init__(self, **kwargs):
        pass

Billy({'a': 1,  'b': 2})

This is in python 3.4.3 and 2.7.6, and I have code that looks identical to this in other scripts that are working just fine. I'm pulling my hair out trying to understand what it wrong here. It keeps giving me a TyperError complaining that I'm using the wrong number of arguments:

TypeError: __init__() takes 1 positional argument but 2 were given

Answer 1

Try adding ** :

>>> Billy(**{'a': 1,  'b': 2})
<__main__.Billy object at 0x00000000023E29B0>

Answer 2

The confusion here is that {'a': 1, 'b': 2} is a single entity which is supplied to the constructor as the first argument, thus it's a positional argument. You will need to either add *args

class Billy:
    def __init__(self, *args, **kwargs):
        pass

or supply it as Billy(a=1, b=2) or do what TigerhawkT3 suggests, adding ** to unpack the dictionary.