Python tips: what are * args and ** kwargs?

Let's look at an example:

def foo(*args, **kwargs):    print 'args = ', args    print 'kwargs = ', kwargs    print '---------------------------------------'if __name__ == '__main__':    foo(1,2,3,4)    foo(a=1,b=2,c=3)    foo(1,2,3,4, a=1,b=2,c=3)    foo('a', 1, None, a=1, b='2', c=3)

The output result is as follows:

Args = (1, 2, 3, 4)

Kwargs = {}

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Args = ()

Kwargs = {'A': 1, 'C': 3, 'B': 2}

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Args = (1, 2, 3, 4)

Kwargs = {'A': 1, 'C': 3, 'B': 2}

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Args = ('A', 1, None)

Kwargs = {'A': 1, 'C': 3, 'B': '2 '}

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As you can see, these two are variable parameters in python. * Args indicates any number of unnamed parameters. It is a tuple. ** kwargs indicates a keyword parameter, which is a dict. When both * args and ** kwargs are used, the * args parameter column must be before ** kwargs, such as foo (a = 1, B = '2', c = 3, if you call this method, a syntax error "SyntaxError: non-keyword arg after keyword arg" is displayed ".

 

You know what * args and ** kwargs are. Another nice usage is to create a dictionary:

    def kw_dict(**kwargs):        return kwargs    print kw_dict(a=1,b=2,c=3) == {'a':1, 'b':2, 'c':3}

In fact, python has a dict class. You can use dict (a = 1, B = 2, c = 3) to create a dictionary.

 

"My life is short. I use python ."

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