CODEWITHSUNDEEP
pythonpython-decorators
Mark van der Wilk
Mark van der Wilk

Reputation: 807

Wrapping a functions taking a variable number of arguments using a decorator

I want to create a decorator which can wrap around functions with different numbers of variables. For example, below I have two functions abc and abcd, taking 2 and 3 arguments respectively. I want the wrapper to take a variable number of arguments in order to deal with this. However, when I run the code, I get TypeError: _wrapper() takes exactly 0 arguments (2 given), as though the **kwargs was ignored.

Why is this, and how do I fix this?

def dec(function):
    def _wrapper(**kwargs):
        print len(kwargs)
        function(**kwargs)
    return _wrapper

@dec
def abc(a, b):
    return a*b

@dec
def abcd(a, b, c):
    return a*b*c

Upvotes: 4

Views: 3941

Answers (1)

Inverse
Inverse

Reputation: 4476

Python has two variable argument variables: *args and **kwargs. args is a list of arguments specified without names (e.g. func(1,2,3)), while kwargs is a dictionary of arguments with names (e.g. func(x=1, y=2, z=3)).

Your code is only accepting the kwargs, so you also need to add the unnamed args:

def dec(function):
    def _wrapper(*args, **kwargs):
        print len(args) + len(kwargs)
        return function(*args, **kwargs)
    return _wrapper

Upvotes: 7

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