Question

Sorry about the title, I couldn’t come up with a clean way to ask my question.

In Python I would like to match an expression ‘c[some stuff]t’, where [some stuff] could be any number of consecutive a’s, b’s, or c’s and in any order.

For example, these work:
‘ct’, ‘cat’, ‘cbbt’, ‘caaabbct’, ‘cbbccaat’

but these don’t:
‘cbcbbaat’, ‘caaccbabbt’

Edit: a’s, b’s, and c’s are just an example but I would really like to be able to extend this to more letters. I’m interested in regex and non-regex solutions.

Answer 1

Not sure how attached you are to regex, but here is a solution using a different method:

from itertools import groupby

words = ['ct', 'cat', 'cbbt', 'caaabbct', 'cbbccaat',  'cbcbbaat', 'caaccbabbt']
for w in words:
    match = False
    if w.startswith('c') and w.endswith('t'):
        temp = w[1:-1]
        s = set(temp)
        match = s <= set('abc') and len(s) == len(list(groupby(temp)))
    print w, "matches" if match else "doesn't match"

The string matches if a set of the middle characters is a subset of set('abc') and the number of groups returned by groupby() is the same as the number of elements in the set.