正过程：

def Test(a, b, c = 3, *args, ** kwarg):
    print(a)
    print(b)
    print(c)
    if args:
        print("arg: ", args)

    if kwarg:
        print("kwarg: ", kwarg)

*arg会把多出来的位置参数转化为tuple

**kwarg会把关键字参数转化为dict

Test(1, 2, 3, 4, 5, keyword1 = "one", keyword2 = "two")
运行结果：
1
2
3
arg:  (4, 5)
kwarg:  {'keyword1': 'one', 'keyword2': 'two'}

逆过程：

def sum(a, b, c):
    return a + b + c

a = [1, 2, 3]

# the * unpack list a 
# 将元组或者列表分解为：1，2，3
print sum(*a)
>> 6

def sum(a, b, c):
    return a + b + c

a = {'a': 1, 'b': 2, 'c': 3}

# the ** unpack dict a
#将字典分解为'a' = 1, 'b' = 2, 'c' = 3
print sum(**a)
>> 6