I have regex to match repeating sequence of word 'abc' separated by spaces.

re.search("(abc \s){3}", "abc abc abc ")

I want to upgrade it to match sequences with 0 or 1 inserted words(words can be different with different lengths). Examples:

"abc abc abc " #match
"abc defgh abc abc " #match
"abc xyz abc abc " #match
"abc abc ghi abc " #match
"abc ghi abc def abc " #not match

Number of repetitions may also vary, it should be applicable to multiple repetitions.

CodePudding user response：

Try this:

/abc \s(([a-z] \sabc)|(abc\s[a-z] )|abc)\sabc \s/

CodePudding user response：

The pattern you're looking for is (abc\s)(?:(?:\1\1)|(?:\w \s\1\1)|(?:\1\w \s))

import re

pattern = r"(abc\s)(?:(?:\1\1)|(?:\w \s\1\1)|(?:\1\w \s))"

bool(re.search(pattern, "abc abc abc "))  # True
bool(re.search(pattern, "abc defgh abc abc "))  # True
bool(re.search(pattern, "abc xyz abc abc "))  # True
bool(re.search(pattern, "abc abc ghi abc "))  # True
bool(re.search(pattern, "abc ghi abc def abc "))  # False

CodePudding user response：

You may use this regex to match:

\b(?!(abc  (?!abc )\w ){2})(?:abc  (?:\w   )?){3}

RegEx Demo

RegEx Details:

• \b: Word boundary
• (?!(abc (?!abc )\w ){2}): Fail the match if there are more than one non-abc words
• (?:: Start a non-capture group
  • abc : Match abc followed by 1 spaces
  • (?:: Start inner non-capture group
    • \w : Match 1 word characters
    • : Match 1 space characters
  • )?: End inner non-capture group. Match this group 0 or 1 times
• ){3}: End outer non-capture group. Repeat this group 3 times