Parameter passing of python function

In this use case, what we are going to discuss is about the parameter passing of functions

The python version I am using is 3.3.2

For functions:

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def fun(arg):

print(arg)

def main():

fun('hello,Hongten' )

​​​

if __name__ == '__main__':

main()

When we pass a parameter to the fun() function, we can print out the passed parameter value information.

The information printed here is:

hello,Hongten

For the following use case:

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def fun(a=1, b=None, c=None, *args):

print('{0},{1},{2},{3}'.format(a, b, c, args))

                                                                                                                               . ()

When the parameters passed are: fun(a='one') and fun('one'), the value is copied to parameter a. The effect of all two parameters is the same:

one,None,None,()

one,None,None,()

Of course we can also assign values ​​to parameters: b, c, *args

such as:

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def fun(a=1, b=None, c=None, *args):

print('{0},{1 },{2},{3}'.format(a, b, c, args))

​​​​​

def​main():

​​fun('one',1,2,('hongten'))

                                                                                                                                         . ('hongten',)

In the above example, we cannot bypass the parameters a, b, c in front of the parameter *args and copy them to *args:

Such as:

def fun(a=1, b=None, c=None, *args):
    print('{0},{1},{2},{3}'.format(a, b, c, args))
      
def main():
    fun(args=('hongten'))
      
if __name__ == '__main__':
    main()

Running effect:

Traceback (most recent call last):

File "E:/Python33/python_workspace/test_fun.py", line 21, in

main()

File "E:/Python33/python_workspace/test_fun.py", line 18, in main

fun(args=('hongten'))

TypeError: fun() got an unexpected keyword argument 'args'

But for parameters: a, b, c, you can use this Assign value in the way

such as:

def fun(a=1, b=None, c=None, *args):
    print('{0},{1},{2},{3}'.format(a, b, c, args))
      
def main():
    fun(c=('hongten'), b=2, a=[1,2,3])
      
if __name__ == '__main__':
    main()

Operating effect:

[1, 2, 3],2,hongten,()