*args 和**kwargs

原文

当函数的参数不确定时，可以使用args 和kwargs，args 没有key值，**kwargs有key值。
这个和Python的函数方法特性有关系.
**kwargs,函数可接受以参数名(key值)配对的无序的参数赋值
*args,有序无名参数数量可变的参数集.

*args

def fun_var_args(farg, *args):  
    print "arg:", farg  
    for value in args:  
        print "another arg:", value  
  
fun_var_args(1, "two", 3) # *args可以当作可容纳多个变量组成的list  

输出:

arg: 1  
another arg: two  
another arg: 3  
**kwargs:

def fun_var_kwargs(farg, **kwargs):  
    print "arg:", farg  
    for key in kwargs:  
        print "another keyword arg: %s: %s" % (key, kwargs[key])  
  
  
fun_var_kwargs(farg=1, myarg2="two", myarg3=3) # myarg2和myarg3被视为key， 感觉**kwargs可以当作容纳多个key和value的dictionary  

输出:

arg: 1  
another keyword arg: myarg2: two  
another keyword arg: myarg3: 3  

另外一种用法

def fun_var_args_call(arg1, arg2, arg3):  
    print "arg1:", arg1  
    print "arg2:", arg2  
    print "arg3:", arg3  
  
args = ["two", 3] #list  
  
fun_var_args_call(1, *args)  

输出:

arg1: 1  
arg2: two  
arg3: 3  

def fun_var_args_call(arg1, arg2, arg3):  
    print "arg1:", arg1  
    print "arg2:", arg2  
    print "arg3:", arg3  
  
kwargs = {"arg3": 3, "arg2": "two"} # dictionary  
  
fun_var_args_call(1, **kwargs)  

输出:

arg1: 1  
arg2:"two"  
arg3:3