CODEWITHSUNDEEP
pythonregex
Phil Fugate
Phil Fugate

Reputation: 26

Create a regex that matches when there are non repeating characters of a particular type

I am trying to create a regex that matches when there are no repeating characters of a particular type and all other characters are ignored. Word length does not matter. Ex.

hippos-R-Y-S <--- Matches
hippos-R-Y-Y <--- Does not match
hippos-R-Y-P <--- Matches

Again, the hippos- text could be anything, but the capital letters that follow have to be in the set of [YRPS]. Thanks for your help!!

Upvotes: 0

Views: 1147

Answers (2)

anubhava
anubhava

Reputation: 784938

You can use this regex based on 2 negative lookaheads to skip matching repeated character in [YRPS] class:

^[^-]+-([YRPS])(?:-(?!\1)([YRPS])(?!.*\2))+$

RegEx Demo

**RegEx Breakup:*

^           # line start
[^-]+       # match 1 or more of any char that is not a -
-           # match literal -
([YRPS])    # match [YRPS] and group it #1
(?:         # start non-capturing group
   -        # match literal -
   (?!\1)   # negative lookahead to assert next char is not same as group #1
   ([YRPS]) # match [YRPS] and group it #2
   (?!.*\2) # negative lookahead to assert next char is not same as group #2
)+          # end non-capture group and + makes it match 1 or more of the same set
$           # end of line

Upvotes: 1

Toto
Toto

Reputation: 91375

This should do the job:

^.*?-([YRPS])-(?!\1)([YRPS])-(?!\1)(?!\2)([YRPS])$

Explanation:

^           : begining of string
  .*?-      : 0 or more any char until dash
  ([YRPS])  : one of the set, captured in group 1
  -         : a dash
  (?!\1)    : negative lookahead, not the same letter as in group 1
  ([YRPS])  : one of the set, captured in group 2
  -         : a dash
  (?!\1)    : negative lookahead, not the same letter as in group 1
  (?!\2)    : negative lookahead, not the same letter as in group 2
  ([YRPS])  : one of the set, captured in group 3
$           : end of string

Upvotes: 1

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