python --- *args和**kwargs

*args和**kwargs

* Args is an array of all parameters; ** kwargs parameter is a dictionary, see specific examples:

def test(a,*args,**kwargs):
    print a
    print args
    print kwargs
test(1,2,3,d='4',e=5)

Output:

1
(2, 3)
{'e': 5, 'd': '4'}

Example 2:

def foo(*args, **kwargs):
    print ('args = ', args)
    print ('kwargs = ', kwargs) 
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)

Output:

args =  (1, 2, 3, 4) 
kwargs =  {} 
--------------------------------------- 
args =  () 
kwargs =  {'a': 1, 'c': 3, 'b': 2} 
--------------------------------------- 
args =  (1, 2, 3, 4) 
kwargs =  {'a': 1, 'c': 3, 'b': 2} 
--------------------------------------- 
args =  ('a', 1, None) 
kwargs =  {'a': 1, 'c': 3, 'b': '2'} 
---------------------------------------

to sum up

These two parameters are variable in python. * args represents unnamed parameters any more, it is a tuple; ** kwargs represents keyword arguments, it is a dict. And use * args and ** kwargs time, * args parameter must be before ** kwargs, like foo(a=1, b='2', c=3, 1, None )this call, it will prompt syntax error“SyntaxError: non-keyword arg after keyword arg”

reference

• Turn: Python: What is * args and ** kwargs