正则表达式仅在同一行中匹配

Question

Sample of the text am trying to solve using regex in Python is as below

it is amamzing to look at the evening sky and the color

color of the sky is blue

color

sky color is blue

Am trying to find up to 3 words previous to the color however I want to extract the words if they are only in the same line

Highlighted is the Output am looking for

it is amamzing to look at the evening  color

color of the sky is blue

color

 color is blue

Code I am using is

((?:\S+\s+){0,4}\b(?=color)\b\s*)

Sample as below

https://regex101.com/r/Q61Hi7/1

This may be a duplicate question, however I couldn't find any answer that solves

Answer 1

Instead of using \\s to match any whitespace, use a literal space to just match spaces. You could add \\t if you want to include that too.

((?:\S+ ){0,4}\b(?=color)\b\s*)

Answer 2

• the \\n is included in \\s that's why you read form different lines, you may use \\t (space + tab)
• for up to 3 words, I'd say {1,3} to get 1, 2 or 3 words ({0,4} can read none and 4 words too)

Result in ((?:\\S+[ \\t]){1,3}\\b(?=color)\\b\\s*) https://regex101.com/r/Q61Hi7/3

Answer 3

Try (?:\\S+ +){0,3}color

Explanation:

(?:...) - non-capturing group

\\S+ - match 1+ of non-whtespace characters (to match a word)

+ - match 1+ spaces (you can include here other whitecharacters, but don't use \\s as it will break your requirement of single line match, because it matches newline character as well)

{0,3} - match preceding pattern between 0 and 3 times

color - match color literally

Demo

Answer 4

You may use

\S+(?:[^\S\r\n]+\S+){0,3}(?=[^\S\r\n]+color\b)

See the regex demo and the Regulex graph :

Details

• \\S+ - 1+ non-whitespace chars
• (?:[^\\S\\r\\n]+\\S+){0,3} - zero to three occurrences of
  • [^\\S\\r\\n]+ - 1+ horizontal whitespaces (assuming line endings are CR/LF)
  • \\S+ - 1+ non-whitespace chars
• (?=[^\\S\\r\\n]+color\\b) - immediately to the right of the current location, there must be 1+ horizontal whitespaces and then a whole word color .

Python demo :

import re
rx = r"\S+(?:[^\S\r\n]+\S+){0,3}(?=[^\S\r\n]+color\b)"
s = "it is amamzing to look at the evening sky and the color\ncolor of the sky is blue\ncolor\nsky color is blue"
print(re.findall(rx, s))
# => ['evening sky and the', 'sky']