python拆包和封包

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python的拆包和封包之 *号在函数形参和实参的区别
1. 在函数形参定义时添加*就是封包过程，封包默认是以元组形式进行封包
2. 在函数实参调用过程添加*就是拆包过程，拆包过程中会报列表或者元组拆成单个元素
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subject = [\"math\", \"chinese\", \'english\', \'physics\', \'history\']


def print_subject_one(sub):
    print(*sub)


def print_subject_two(*sub):
    print(sub)


def print_subject_three(*sub):
    print(*sub)


def print_subject_four(*sub):
    print(*sub)


def print_subject_five(*sub):
    print(sub)


print_subject_one(subject)  # math chinese english physics history
print_subject_two(subject)  # ([\'math\', \'chinese\', \'english\', \'physics\', \'history\'],)
print_subject_three(subject)  # [\'math\', \'chinese\', \'english\', \'physics\', \'history\']
print_subject_four(*subject)  # math chinese english physics history
print_subject_five(*subject)  # (\'math\', \'chinese\', \'english\', \'physics\', \'history\')


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python的拆包和封包之 **号在函数形参和实参的区别
1. 在函数形参定义时添加**就是封包过程，封包默认是字典形式进行封包,
2. 在函数实参调用过程添加**就是拆包过程，通常在存在关键字参数的函数去使用**对字典进行拆包
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hobby = {\"jack\": \"dance\", \"henry\": \"basketball\", \"jenny\": \"swimming\", \"richard\": \"reading\"}


def print_hobby_one(**bby):
    print(bby)


def print_hobby_two(**bby):
    print(bby)


def print_hobby_three(**bby):
    if \"jack\" in bby:
        print(\'jack like dance\')
    if \"jenny\" in bby:
        print(\"jenny like swimming\")


print_hobby_one(**hobby)  # {\'jack\': \'dance\', \'henry\': \'basketball\', \'jenny\': \'swimming\', \'richard\': \'reading\'}
print_hobby_two(jack=\'dance\', henry=\'basketball\')  # {\'jack\': \'dance\', \'henry\': \'basketball\'}
print_hobby_three(**hobby)  # jack like dance  jenny like swimming


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python的拆包和封包之 * 在其它场景的应用
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a, *_, c = [1, 2, 3, 4, 5, 6]  # a=1, c=6
print(a)  # a=1, c=6
print(c)  # a=1, c=6


a, b, *_ = [1, 2, 3, 4, 5, 6]
print(a)  # a=1
print(b)  # b=2


# 一行代码搞定两个变量交换赋值
x = 10
y = 20

x, y = y, x
print(x)  # x = 20
print(y)  # y = 10

来源：https://www.cnblogs.com/zengmuyao/p/16353664.html
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