传递未知的args和kwargs在python中运行

Question

I have an object that takes in a function name func, args, and kwargs, and at some point runs

func(*args, **kwargs)

The issue is, if func requires no args/kwargs, args/kwargs default to None, which leads to a TypeError. For example, if the function required no parameters, args, kwargs default to None:

def test():
    pass

args = None

kwargs = None

test(*args, **kwargs)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-b9618694fbf2> in <module>()
----> 1 test(*args, **kwargs)

TypeError: test() argument after ** must be a mapping, not NoneType

I'm sure there's a good way to solve this without cascading if statements checking if args/kwargs exist, each with its own function call, but I'm not sure how. The main goal is to pass a function, and its unknown parameters to an object, which will then use them in a method later.

Edited: added an example for clarity

Answer 1

The issue is, if func requires no args/kwargs, args/kwargs default to None, which leads to a TypeError.

This is not true:

def func1(*args, **kwargs)
    print args, kwargs

will print

() {}

In reverse,

def func2(): pass

can be perfectly called with

func2(*(), **{})

So just change your args and kwargs variables and you're fine.

Answer 2

Avoid to default your args and kwargs to None .

• args should be a tuple : args = ()
• kwargs should be a dictionnary : kwargs = {}