正则表达式中的前瞻 [英] Lookahead in Regex

问题描述

我正在尝试使用正则表达式从包含几篇文章的文件中提取场所.我知道场地以For/From开头，后跟日期，以星期几或作者的名字开头(如果缺少日期)，我编写了以下正则表达式以匹配场地，但是，直到作者的名字，这意味着如果该文章有日期，日期也将出现在场地中.

I am trying to extract venue from a file which contains several articles using regex. I know that the venue starts with either For/From and is followed by date which starts with a day of the week or author's name if the date is missing, I wrote the following regex to match the venue, however it always matches everything till the author's name which means the date also comes in the venue if that article has a date.

"""((?<=\n)(?:(?:\bFrom\b)|(?:\bFor\b)).*?(?=(?:(?:Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Sunday)|(?:[A-Z]+))))""".r

如果遇到我的代码为什么不匹配日期，而是继续匹配作者姓名[A-Z].

Why is my code not matching the days if it is encountered but rather goes ahead to match [A-Z] which is the author's name.

输入:国家间敌对行动的后果

Input: "The Consequences of Hostilities Between the States

来自纽约邮包.

1787年11月20日，星期二.

Tuesday, November 20, 1787.

汉密尔顿

致纽约州人民:"

行"1787年11月20日，星期二".是可选的，可能不会在所有文章中都出现.我希望输出为来自纽约邮包". 对于没有日期的文章，我得到了正确的输出，但是从纽约邮包"中得到了输出.

The line "Tuesday, November 20, 1787." is optional and may not occur in all articles. I want the output to be "From the New York Packet." I am getting the correct output for articles that do not have a date, however I am getting the output "From the New York Packet.

1787年11月20日，星期二."以了解包含日期的文章.

Tuesday, November 20, 1787." for articles that contain the date.

推荐答案

您只需要捕获以For或From开头的整行，因此您可以简单地使用以下代码:

You only need to capture the entire line that starts with For or From, so you can simply use this:

^(For|From).*$

^和$将匹配项固定到行的开头和结尾，而.*匹配之间的所有内容.

The ^ and $ anchor the match to the start and end of the line, and the .* matches everything inbetween.

在这里，尝试一下，并附上您喜欢的任何示例.

Here, try it out with whatever examples you like.

如果这需要更复杂，我将更新答案.

If this needs to be more complicated, I'll update my answer.

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