Python注意参数传递

注意传递参数的时候，不好传递空列表，不然有时会出现一些无法理解的问题

def add(a, b):
    a += b
    return a


class company(object):
    def __init__(self, name, stuff=[]):
        self.name = name
        self.stuff = stuff

    def add(self, stuff_name):
        self.stuff.append(stuff_name)

    def remove(self, stuff_name):
        self.stuff.remove(stuff_name)


def bad_append(new_item, a_list=[]):
    a_list.append(new_item)
    return a_list


if __name__ == '__main__':
    a = 1
    b = 2
    print(add(a, b))
    print(a)
    print(b)

    a = [1, 2]
    b = [3, 4]
    print(add(a, b))
    print(a)
    print(b)

    a = (1, 2)
    b = (3, 4)
    print(add(a, b))
    print(a)
    print(b)

    com2 = company("com2")
    com2.add("bobby")
    print(com2.stuff)

    com3 = company("com3")
    com3.add("bobby5")
    print(com2.stuff)
    print(com3.stuff)

    print(bad_append('1'))
    print(bad_append('2'))
输出
3
1
2
[1, 2, 3, 4]
[1, 2, 3, 4]
[3, 4]
(1, 2, 3, 4)
(1, 2)
(3, 4)
['bobby']
['bobby', 'bobby5']
['bobby', 'bobby5']
['1']
['1', '2']

所以下次传列表参数的时候，记住不要传递[]，而是可以传为None
如：

def bad_append(new_item, a_list=None):
	if a_list == None:
		a_list = []
    a_list.append(new_item)
    return a_list

这样就可以了。