Python 调用子类函数以减少代码复制

我希望通过在父类中使用公共代码来减少子类中的代码复制，但仍然需要执行一些特定的处理，这些处理会根据子类的不同而变化。我知道从父母那里给孩子打电话是不好的。如何完成代码缩减？（或者我应该试一试吗？）

这是一个例子：

class Address:

    def __init__(self, street, city, postal_code):

        self._street = street
        self._city = city
        self._postal_code = self.valid_postal_code(postal_code)

    def valid_postal_code(self, postal_code):
        """ Returns a validated postal code """
        #
        # A big bunch of code common to all postal codes
        #

        if child == Usa:
            return Usa.valid_postal_code(postal_code)
        else:
            return Canada.valid_postal_code(postal_code)    

class Usa(Address):

    def valid_postal_code(self, postal_code):
        """ Returns a validated US zip code """
        # Must be 5 digits or 5 digits plus dash 4 digits
        if len(postal_code) != 5 and len(postal_code) != 10:
            raise Exception("Bad postal code")

        return postal_code


class Canada(Address):

    def valid_postal_code(self, postal_code):
        """ Returns a validates Canadian postal code """
        # Must be A#A #A#
        if len(postal_code) == 6:
            postal_code = postal_code[0:3] + " " + postal_code[3:3]
        if len(postal_code) != 7:
            raise Exception("Bad postal code")

        return postal_code.upper()

---

每个重写方法都应该调用父方法

class Address:

    def __init__(self, street, city, postal_code):

        self._street = street
        self._city = city
        self._postal_code = self.valid_postal_code(postal_code)

    def valid_postal_code(self, postal_code):
        """ Returns a validated postal code """
        #
        # A big bunch of code common to all postal codes
        #
        ...


class Usa(Address):

    def valid_postal_code(self, postal_code):
        """ Returns a validated US zip code """

        # Must be 5 digits or 5 digits plus dash 4 digits
        if not super().valid_postal_code(postal_code) or len(postal_code) != 5 and len(postal_code) != 10:
            raise Exception("Bad postal code")

        return postal_code


class Canada(Address):

    def valid_postal_code(self, postal_code):
        """ Returns a validates Canadian postal code """
        # Must be A#A #A#
        if len(postal_code) == 6:
            postal_code = postal_code[0:3] + " " + postal_code[3:3]
        if not super().valid_postal_code() or len(postal_code) != 7:
            raise Exception("Bad postal code")

        return postal_code.upper()

---

有两种可能性：

• 让父代码包含公共部分，子代码包含细节
  • 父级必须返回中间结果

或

• 有两个父方法，其中一个是存根并由子方法重写
  • 父级将中间结果传递到存根中

第二种方法类似于：

class Address:

    def __init__(...):

    def valid_postal_code(self, postal_code):
        """ Returns a validated postal code """
        #
        # A big bunch of code common to all postal codes
        #
        return self._validate_postal_code(postal_code)

    def _validate_postal_code(self, postal_code):
        raise NotImplementedError


class Usa(Address):

    def _validate_postal_code(self, postal_code):
        """ Returns a validated US zip code """
        # Must be 5 digits or 5 digits plus dash 4 digits
        if len(postal_code) != 5 and len(postal_code) != 10:
            raise Exception("Bad postal code")
        return postal_code


class Canada(Address):

    def _validate_postal_code(self, postal_code):
        """ Returns a validates Canadian postal code """
        # Must be A#A #A#
        if len(postal_code) == 6:
            postal_code = postal_code[0:3] + " " + postal_code[3:3]
        if len(postal_code) != 7:
            raise Exception("Bad postal code")
        return postal_code.upper()

---

除了邮政编码之外，美国和加拿大的地址没有任何共同之处。基本上，

Address。有效的邮政编码

只有一个通用的占位符定义（如

pass

或

return True

或

return False

），每个子类都必须用一个适当的定义覆盖它。让所有邮政编码共有的一大串代码成为一个公共部分，但是子类中应该保留不同的验证逻辑每个子类应该通过

super（）调用父类。有效的\u postal\u code（）

而不是调用子实现的父类，因为父类不一定知道（或关心）哪些子类存在。