Python regex: Alternation for sets of words

Question

We know \\ba\\b|\\bthe\\b will match either word \"a\" or \"the\"
I want to build a regex expression to match a pattern li

Answer 1

As I understand you want some regex like this:

(?:a|the|one)\s+(?:reason|reasons)\s+(?:for|of)

It's so simple, just combine them by using groups.

see: DEMO

Note Your requirement above, its sound is not so strict for me, in case that you want to modify something by yourself, let's consider the explanation below

Explanation

(?:abc|ijk|xyz)

Any word abc, ijk or xyz which grouped by non-capture group (?:...) means this word will not capture to regex variable $1, $2, $3, ....

\s+

This is word delimiter which here I set it as any spaces, + stands for 1 or more.