Python regex - match and replace unknown length of elements

Question

I have the following problem. Often data exists in a form:

IF X = (A OR B OR C OR D)

or

IF X = (Aa OR Bb OR Cc)

where 'OR' are separators and letters are values - but, number of elements in list is undefined. I want to change it to:

IF X = 'A' OR X = 'B' OR X = 'C' OR 'D'

and, accordingly:

IF X = 'Aa OR X = 'Bb' OR X = 'Cc'

I have completely no idea how to solve it by regular expression or even how to ask properly about the solution.

How to do it?

Also is it just `OR`? No `AND`s? You need to provide more details. Also is that a string or code? Is it always uppercase? — Error - Syntactical Remorse, Nov 05 '19 at 13:58
Please give example input and output. Your explanation is too vague — Jab, Nov 05 '19 at 13:59
A little [modification of @MichałTurczyn regex](https://regex101.com/r/1HWbjU/3) could spare removement of `X = ` — bobble bubble, Nov 05 '19 at 14:14
Python simply has an `in` operator, thus : `if val in [A,B,C,D]`. If you're testing membership a lot, use a set, it will be faster. — smci, Jun 09 '20 at 08:47
But when you show us `IF X = (A OR B OR C OR D)`, is that just pseudocode, or do you mean you're literally trying to parse SQL code? — smci, Jun 09 '20 at 08:48
This is a dupe of [How to test multiple variables against a value?](https://stackoverflow.com/questions/15112125/how-to-test-multiple-variables-against-a-value) — smci, Jun 09 '20 at 08:49

score 4 · Accepted Answer · answered Nov 05 '19 at 14:02

You could use (\w+)(?= OR|\)$) after removing X = at the beginning:

Explanation:

(\w+) - match one or more of word-characters and store it inside capturing group,

(?= OR|\)$) - positive lookahead with alternation: assert what follows is OR or ) and end of the string

Replace it with X = \1, meaning replacing with X = followed by first capturing group.

1 Answers1