Python在类中设置变量类型答案

【问题标题】：Python set variables types inside classPython在类中设置变量类型
【发布时间】：2021-12-25 11:41:05
【问题描述】：

我正在尝试为我的类变量设置可接受的内置类型。如果给定类型不正确，我想抛出异常。有没有比使用 isinstance() 的 setter 更好的方法？

我的第一次尝试：

class Address:
    city: str
    building_number: str or int
    apartment_number: int
    street: str

    def __init__(self, city, building_number, apartment_number, street):
        self.city = city
        self.building_number = building_number
        self.apartment_number = apartment_number
        self.street = street

不幸的是，无论类型如何，它都会编译。

我的第二次尝试：

class Address:
    def __init__(self, city: str, building_number: str, apartment_number: int, street: str):
        self.city = city
        self.building_number = building_number
        self.apartment_number = apartment_number
        self.street = street

这个在创建类时实际上显示了错误的类型，但它编译时没有抛出任何错误或消息。

【问题讨论】：

标签： python class types typing

【解决方案1】：

isinstance() 是一种安全的方法，但如果您只想输入更少，您可以使用由“+”运算符完成的类型检查，如下所示

class Address:
    city: str
    building_number: str or int
    apartment_number: int
    street: str

    def __init__(self, city:str, building_number:str, apartment_number:int, street:str):
        self.city = "" + city
        self.building_number = "" + building_number
        self.apartment_number = 0 + apartment_number
        self.street = "" + street

x = Address(1, "a", "b", "c")

而且stacktrace消息是有意义的：

Traceback (most recent call last):
  File "test.py", line 14, in <module>
    x = Address(1, "a", "b", "c")
  File "test.py", line 9, in __init__
    self.city = "" + city
TypeError: must be str, not int

【讨论】：

【解决方案2】：

我试过了，没有报错：

class Address:
    def __init__(self, city: str, building_number: str, apartment_number: int, street: str):
        self.city = city
        self.building_number = building_number
        self.apartment_number = apartment_number
        self.street = street

a = Address(1, "asassa", "shoudbeanint", "asas")

print (a.city)
print (a.apartment_number)

【讨论】：