Python's variable parameter *args,**kwargs and differences

You can often see *args and **kwargs in Python's function arguments, which is the magic parameter of Python, a variable parameter that supports passing in multiple parameters, and look at the difference between them.

*args represents any number of unnamed parameters, it is a tuple;**kwargs to represent the keyword parameter, it is a dict. And when using both *args and **kwargs, you must *args the parameter columns before **kwargs, such as foo (a=1, b= ' 2′, c=3, a ', 1, None,), which prompts for syntax errors "SyntaxError: Non-keyword arg after keyword arg ".

For example, use the **kwargs variable parameter to create a dictionary:

def kw_dict (**kwargs):
Return Kwargs

Then the effect of the function defines a dictionary, kw_dict (a=1,b=2,c=3) and {' A ': 1, ' B ': 2, ' C ': 3} is equivalent.

Python's variable parameters are also called dynamic parameters, and look at the simple basic usage of *args and **kwargs.

def alias (*args, **kwargs):
Print (' args= ', args)
Print (' kwargs= ', Kwargs)

Alias (3, 3, 3,a= ' Hello ', b=3,c= ' C ')

The operation effect is as follows:

Tantengdemacbook-pro:learn-python tanteng$ Python3 args_kwargs.py
Args= (3, 23, 3, 3)
kwargs= {' A ': ' Hello ', ' B ': 3, ' C ': ' C '}
Args output is Tupple Ganso, Kwargs is a dictionary