python中的*arg和**kwargs

def example(pram):
    print(pram)


def example2(param, *args, **kwargs):
    print(param)
    if args:
        print(args)
    if kwargs:
        print(kwargs)


#一个不设定参数个数的加法函数
def sum(*args):
    sum = 0
    for a in args:
        sum += a
    return sum


#控制关键字参数的个数,可以用"*"作为分割参数
def person(param, *, keyword1, keyword2):
    print(param, keyword1, keyword2)


############################################3
#反向思维用法
def another_sum(a, b, c):
    print(a + b + c)

if __name__ == "__main__":
    example("hello world!")    #hello world!
    #该情况下会报错
    # example("hello world!", "honey")

    #*args, **kwargs为空也不行影响函数运行
    example2("hello world!")    #hello world!

    #pram是位置参数;*arg会把多的位置参数转成元组;**kwargs必须要带上关键字,比如"word1=",关键字参数会被转成字典.
    example2("hello world!", "honey", "hi", word1="happy new year", word2="red packet") #hello world!
                                                                                                 #(‘honey‘, ‘hi‘)
                                                                                                 #{‘word1‘: ‘happy new year‘, ‘word2‘: ‘red packet‘}

    # 一个不设定参数个数的加法函数
    print(sum(1, 2, 3, 4))  #10

    # 控制关键字参数的个数
    person("name:", keyword1="qin", keyword2="fen") #name: qin fen

    ############################################3
    # 反向思维
    arg1 = [1, 2, 3]
    #把lis进行了拆分
    another_sum(*arg1)    #6

    #此处的键要和形参一致,必须为‘a‘,‘b‘,‘c‘
    kwargs1 = {"a":1, "b":2, "c":3}
    another_sum(**kwargs1)    #6