Python类的__repr__方法中f-string出现SyntaxError问题求助

你的代码：

class Book:
    all = []
    def __init__(self, ISBN, title, subject, publisher, language, number_of_pages):
        self.__ISBN = ISBN
        self.__title = title
        self.__subject = subject
        self.__publisher = publisher
        self.__language = language
        self.__number_of_pages = number_of_pages
        self.__authors = []

        Book.all.append(self)

    def __repr__(self):
        return f"Title {self.__title} Subject {self.__subject}"

b = Book(23498723,"this","fiction","penguin","en",196)

运行时出现的错误：

return f"Title {self.__title} Subject {self.__subject}"
                                                          ^
SyntaxError: invalid syntax

错误原因 #

问题出在代码里的"——这是HTML的双引号转义字符，但Python无法识别它。

Python中字符串的边界需要用原生双引号"或单引号'标识，你用"替代正常引号后，Python会把它当成普通字符串内容，导致f-string的结构完全混乱：它找不到正确的引号来闭合字符串，因此抛出语法错误。

修复后的代码 #

把所有"替换成原生双引号"即可：

class Book:
    all = []
    def __init__(self, ISBN, title, subject, publisher, language, number_of_pages):
        self.__ISBN = ISBN
        self.__title = title
        self.__subject = subject
        self.__publisher = publisher
        self.__language = language
        self.__number_of_pages = number_of_pages
        self.__authors = []

        Book.all.append(self)

    def __repr__(self):
        return f"Title {self.__title} Subject {self.__subject}"

b = Book(23498723,"this","fiction","penguin","en",196)

内容的提问来源于stack exchange，提问作者Raj