Regex回顾问题

Question

我在其他文章中看到，在执行(?<!X|Y|Z)时，这是解决不固定宽度模式问题的正确方法，但并不适合我。

我正在尝试以下几种方法

re.search(r'\b(?:(?<!Yummy)|(?<!Xoo))\bfoo\b', "Yummy foo", flags=re.UNICODE) is not None => True
re.search(r'\b(?:(?<!Yummy)|(?<!Xoo))\bfoo\b', "Xoo foo", flags=re.UNICODE) is not None => True
re.search(r'\b(?:(?<!Yummy)|(?<!Xoo))\bfoo\b', "other Yummy  foo someone", flags=re.UNICODE) is not None => True

当它应该返回False时，它总是返回True。现在，如果我删除了or \\，它就会正常工作。

re.search(r'\b(?:(?<!Yummy))\bfoo\b', "Yummy foo", flags=re.UNICODE) is not None => False
re.search(r'\b(?<!Yummy)\bfoo\b', "Yummy foo", flags=re.UNICODE) is not None => False
re.search(r'\b(?<!Yummy)\bfoo\b', " Yummy  foo", flags=re.UNICODE) is not None => False
re.search(r'\b(?<!Yummy)\bfoo\b', "other Yummy foo someone", flags=re.UNICODE) is not None => False
re.search(r'\b(?<!Yummy)\bfoo\b', "foo someone", flags=re.UNICODE) is not None => True
re.search(r'\b(?<!Yummy)\bfoo\b', "foo", flags=re.UNICODE) is not None => True

有什么建议吗？

Answer 1

您不需要使用替换，因为后面的查找是零宽度断言，您可以这样写：

re.search(r'\b(?<!\bYum)(?<!\bXooop)\s+foo\b', "Yum foo", flags=re.UNICODE)
            ^ ^         ^
            | |         |
            +-+---------+---These three assertions are tested at the same
                            position (i.e. immediatly before the \s+ match.
                            You can put them in any order you want, they are
                            only checks and don't eat characters.