python *args ** kwargs

argv:

命令行参数List，第一个元素是程序本身路径，如需获取参数可用argv[1：]

 

*args and * kwargs

简单地说：*args去匹配没有指定参数名的参数，即列举出来的参数agr1,arg2,agr3。**kwargs 去匹配指定参数名的参数，形如：arg1="arg1",arg2="arg2",arg3="arg3"

关于*args and * kwargs的使用看下面几个例子：

>>> def print_everything(*args):
        for count,thing in enumerate(args):
...         print "%d. %s" %(count, thing)
...
>>> print_everything('apple', 'banana', 'cabbage')
0. apple
1. banana
2. cabbage

上面这个例子，对*args进行解析的时候用到了“for a, b in enumerate (data)”.  这里data是list或者tuple， a则自动对应index， b自动对应value。

>>> def table_things(**kwargs):
...     for name,value in kwargs.items():
...         print name, "=", value
...
>>> table_things(apple = 'fruit', cabbage = 'vegetable')
cabbage = vegetable
apple = fruit

这个例子中显然参数是一个具有key和value的键值对，访问的时候需要用到“for a, b in dic.items()”.

>>> def print_three_things(a, b, c):
...     print "a =", a, "& b =", b, "& c =", c
...
>>> mylist = ['aardvark', 'baboon', 'cat']
>>> print_three_things(*mylist)
a = aardvark & b = baboon & c = cat

请看下面列子，就能明白这两个参数的含义：

>>> def printargs(*arg,**kwargs):
print arg,
print kwargs

>>> printargs("a","b",c="1",d="2")
('a', 'b') {'c': '1', 'd': '2'}
>>>