按句点分隔句子，后跟一个大写字母

Question

I'm trying to find a regex that will split a piece of text into sentences at . / ? / ! that is followed by a space that is followed by a capital letter.

"Hello there, my friend. In other words, i.e. what's up, man."

should split to:

Hello there, my friend| In other words, i.e. what's up, man|

I can get it to split on . / ? / ! , but I have no luck getting the space and capital letter criteria.

What I came up with:

.split("/. \s[A-Z]/")

Answer 1

Split a piece of text into sentences based on the criteria that it is a ./?/! that is followed by a space that is followed by a capital letter.

You may use a regex based on a lookahead:

s = "Hello there, my friend. In other words, i.e. what's up, man."
puts s.split(/[!?.](?=\s+\p{Lu})/)

See the Ruby demo . In case you also need to split with the punctuation at the end of the string, use /[!?.](?=(?:\\s+\\p{Lu})|\\s*\\z)/ .

Details :

• [!?.] - matches a ! , ? or . that is...
• (?=\\s+\\p{Lu}) - (a positive lookahead) followed with 1+ whitespaces followed with 1 uppercase letter immediately to the right of the current location.

See the Rubular demo .

NOTE : If you need to split regular English text into sentences, you should consider using existing NLP solutions/libraries. See:

• Pragmatic Segmenter
• srx-english

The latter is based on regex, and can easily be extended with more regular expressions.

Answer 2

Apart from Wiktor's Answer you can also use lookarounds to find zero width and split on it.

Regex: (?<=[.?!]\\s)(?=[AZ]) finds zero width preceded by either [.?!] and space and followed by an upper case letter.

s = "Hello there, my friend. In other words, i.e. what's up, man."
puts s.split(/(?<=[.?!]\s)(?=[A-Z])/)

Output

Hello there, my friend. 
In other words, i.e. what's up, man.

Ruby Demo

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Update: Based on Cary Swoveland's comment .

If the OP wanted to break the string into sentences I'd suggest (?<=[.?!])\\s+(?=[AZ]) , as it removes spaces between sentences and permits the number of such spaces to be greater than one