正则表达式：不提取可选令牌

Question

我想从这样的句子中提取单词：

Image

现在，我希望在句子的末尾有一些可选的东西：

I want to (?P<activity>([a-zäöüß\s]+?)+)
I want to have a beer 
-> activity: have a beer

如何更改正则表达式，以便I want to (?P<activity>([a-zäöüß\s]+?)+)(?: with my friends)? I want to have a beer with my friends -> have a beer with my friends 不会包含在活动中？

Answer 1

如果你知道在“和我的朋友”之后别的什么就会出现，你可以尝试一个非贪婪的量词并匹配句末：

I want to (?P<activity>([a-zäöüß\s]+?)+?)(?: with my friends)?$

示例：https://regex101.com/r/MG4Ga5/1

否则，也许你可以使用前瞻：

I want to(?P<activity>((?= with my friends)|(\s[a-zäöüß]+))+)

示例：https://regex101.com/r/MG4Ga5/2

Answer 2

您可以使用positive lookahead检查后面的内容是with my friends还是行$的结尾，如果您想将其设为可选项。

I want to (?P<activity>[a-zäöüß\s]+?)(?= with my friends|$)

<强>解释

• 匹配I want to
• 在名为activity (?P<activity>
的命名捕获组中进行匹配
• 您的角色设置一次或多次[a-zäöüß\s]+
• 让它非贪婪?
• 关闭指定的捕获组)
• 断言以下内容为with my friends或行尾(?= with my friends|$)