无法让正则表达式正确处理括号

Question

为这个模糊的标题道歉

我想找一个正则表达式来搜索并确定如下内容：

"Brand New Song [Demonstration]"

通过使用re.search()在字符串的某处找到“[Demonstration]”。下面是一个我认为应该返回True的示例：

bool (re.search (r"\b\[Demonstration\]\b", "Brand New Song [demonstration]", re.IGNORECASE))

更简单的是，它也返回False：

bool (re.search (r"\b\[\b", " [ "))

我一直使用\b作为捕获字符串的开头和结尾，因为它应该表示单词（as per documentation here)）开头或结尾的任何空格字符串，我看不出我搞砸了什么

继续迷惑，以下返回True：

bool (re.search (r"\b\[\b", "_[_"))

这同样令人困惑，因为\b被定义为“…空格或非字母数字、非下划线字符。”所以，请帮我找出我可能遗漏的愚蠢细节，谢谢

Answer 1

您需要从模式中删除单词边界\b

>>> import re
>>> s = 'Brand New Song [demonstration]'
>>> bool(re.search (r'\[Demonstration\]', s, re.IGNORECASE))
True

单词边界不使用任何字符，它断言在一侧有单词字符，而在另一侧没有。如regular-expressions.info documentation中所述：

There are three different positions that qualify as word boundaries:

• Before the first character in the string, if the first character is a word character.
• After the last character in the string, if the last character is a word character.
• Between two characters in the string, where one is a word character and the other is not a word character.