python的*args與**kwargs

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1. *args 允許將一個非索引值對的可變數量的參數列表（元組）傳遞給一個函數。

>>> def add(*args):...     return sum(args)...>>> add(1,2,3,4)10>>> a = (1,2,3,4)>>> add(a) # 錯誤，等價於sum(((1,2,3,4),)),即將元組a與0相加Traceback (most recent call last):  File "<stdin>", line 1, in <module>  File "<stdin>", line 2, in addTypeError: unsupported operand type(s) for +: ‘int‘ and ‘tuple‘>>> add(*a)10>>> sum(((1,2,3,4),))Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: unsupported operand type(s) for +: ‘int‘ and ‘tuple‘

 

2. **kwargs 允許將一個索引值對的可變數量的參數字典傳遞給一個函數。

>>> def add(**kwargs):...     return sum(kwargs.values())...>>> add(a=1,b=2,c=3)6

 

綜合：

>>> def f(arg,*args,**kwargs):...     print(arg)...     print(args)...     print(kwargs)...>>> f(1,*(1,2,3,4),**{"a":1,"b":2,"c":3})1(1, 2, 3, 4){‘b‘: 2, ‘c‘: 3, ‘a‘: 1}>>> f(1,1,2,3,4,a=1,b=2,c=3) # 與上面效果一樣

 

 

調用時

def func(a,b,c,d):    print(a,b,c,d)args = (1,2,3,4)func(*args)1,2,3,4def func(a,b,c,d):    print(a,b,c,d)kargs = {‘a‘:1, ‘b‘:2, ‘c‘:3, ‘d‘:4}func(**kargs)1,2,3,4

 

python的*args與**kwargs