python中函数的收集参数

 

1、

>>> def a(*xxx):
    print("total length is %d" % len(xxx))
    print("the second element is :",xxx[1])

    
>>> a("aaa","bbb","ccc","ddd","eee","fff")
total length is 6
the second element is : bbb

 

>>> def a(*xxx,m):
    print("collection parameter is:",xxx)
    print("keyword parameter is :",m)

    
>>> a(1,2,3,4,5)
Traceback (most recent call last):
  File "<pyshell#616>", line 1, in <module>
    a(1,2,3,4,5)
TypeError: a() missing 1 required keyword-only argument: 'm'
>>> a(1,2,3,4,m = 5)      ## 收集参数之外的参数使用关键字参数
collection parameter is: (1, 2, 3, 4)
keyword parameter is : 5

>>> def a(*xxx,m = 5):         ## 收集参数之外的参数使用默认参数
    print("collection parameter is :",xxx)
    print("keyword parameter is :", m)

    
>>> a(1,2,3,4,5,6)
collection parameter is : (1, 2, 3, 4, 5, 6)
keyword parameter is : 5

 

2、

>>> def a(*xxx):   ## 单星号收集参数打包为元组
    print(type(xxx))

    
>>> a(111,222,333,444)   
<class 'tuple'>
>>> def b(**xxx):   ## 双型号收集参数打包为字典
    print(type(xxx))

    
>>> b(a = "1111",b = "2222",c = "3333")
<class 'dict'>