Python中*args 和**kwargs的用法

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。

*args

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

result:

arg: 1
another arg: two
another arg: 3

**kwargs:

def fun_var_kwargs(farg, **kwargs):
    print("arg: %s" % ( 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

result:

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

也可以用下面的形式：

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

result:

arg1: 1
arg2: two
arg3: 3

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

result:

arg1: 1
arg2:"two"
arg3:3