python 一个经典的参数错误

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

class Company:
    def __init__(self, name, staffs=[]):
        self.name = name
        self.staffs = staffs
    def add(self, staff_name):
        self.staffs.append(staff_name)
    def remove(self, staff_name):
        self.staffs.remove(staff_name)

if __name__ == "__main__":
    com1 = Company("com1", ["bobby1", "bobby2"])
    com1.add("bobby3")
    com1.remove("bobby1")
    print (com1.staffs)

    com2 = Company("com2")
    com2.add("bobby")
    print(com2.staffs)

    print (Company.__init__.__defaults__)

    com3 = Company("com3")
    com3.add("bobby5")
    print (com2.staffs)
    print (com3.staffs)
    print (com2.staffs is com3.staffs)

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

['bobby2', 'bobby3']
['bobby']
(['bobby'],)
['bobby', 'bobby5'] # com2.staffs

['bobby', 'bobby5'] # com3.staffs
True

、、、、、

com2.staffs和com3.staffs使用的同一个内存空间，，这是python内部处理机制造成的，默认的staffs是一个可变对象，所以当传递对象参数到函数中是注意是否是可变对象