Python中的多态性

问题描述

class File(object):
    def __init__(self, filename):
        if os.path.isfile(filename):
            self.filename = filename
            self.file = open(filename, 'rb')
            self.__read()
        else:
            raise Exception('...')

    def __read(self):
        raise NotImplementedError('Abstract method')

class FileA(File):
    def __read(self):
        pass

file = FileA('myfile.a')

# NotImplementedError: Abstract method

我的问题:怎么了?如何将我的代码修复到 FileA 使用 FileA.__read() 而不是 File.__read() 来读取文件?:S

My question: what's wrong? How I can fix my code to FileA use FileA.__read() to read the file instead of File.__read()? :S

提前谢谢你.

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解决方案

用双下划线前缀属性不会使属性私有，它只会使多态性变得不可能，因为属性名称与 当前 类名.改为将其更改为单个下划线前缀.

Prefixing an attribute with double underscores doesn't make the attribute private, it simply makes polymorphism impossible because the attribute name gets mangled with the current class name. Change it to a single underscore prefix instead.