CODEWITHSUNDEEP
regexpython-2.7regex-lookarounds
Kyrubas
Kyrubas

Reputation: 897

regex lookaround and match IF

I'm a bit stuck on trying to figure out how to get lookaround to work for me in regards to an if-else type situation. When I try to implement the if-else idiom on this site I end up with an error. Here's what I have:

MCV(1|0)(\d)(?<!1)\1[0-6]|[0-9]

And this is an example of what I'm trying to match

These

MVC123 MVC034 MVC001 MVC196

Not these

MCV197 MCV000 MCV876

Thus matching where MCV appears and the number component ranges from 1-196

Upvotes: 1

Views: 59

Answers (2)

ndnenkov
ndnenkov

Reputation: 36110

Here is your regex broken down:

MCV(1|0)(\d)(?<!1)\1[0-6]|[0-9]
  1. MCV - match MCV literally
  2. (1|0) - match 1 or 0
  3. (\d) - match a digit
  4. (?<!1) - make sure that last digit wasn't a 1
  5. \1 - match exactly what the first group matched (aka if (1|0) matched 1 - match 1, otherwise - 0)
  6. [0-6] - match a digit from 0 to 6
  7. |[0-9] - alternatively, match all of the above or just a digit from 0 to 9

As to what a real solution would be:

MVC(00[1-9]|0[1-9]\d|1[0-8]\d|19[0-6])

The 1-196 part:

  1. 00[1-9] - if we start with 00, the third digit shouldn't be a 0, aka 1 to 9
  2. 0[1-9]\d - if we start with 0 and a second digit, which isn't a 0 then any digit is acceptable for third position, aka 10 to 99
  3. 1[0-8]\d - if we start with 1 and a second digit, which isn't 9 then any digit is acceptable for third position, aka 100 to 189
  4. 19[0-6] - if we start with 19 then only digits from 0 to 6 are acceptable for third position, aka 190 to 196

Upvotes: 1

anubhava
anubhava

Reputation: 785761

You can use this regex:

\bMVC(0*[1-9][0-9]?|1[0-8][0-9]|19[0-6])\b

RegEx Demo

Upvotes: 1

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