Recursive alphabetical combinations

rec_alph.py

import string
import itertools as it

chars=list(string.ascii_lowercase)

def gen_expansion(inp, length=1):
    if not length: 
        return inp
    if isinstance(inp, str):
        accodati = [inp+c for c in chars]
        if length == 1: 
            return accodati
        else:
            return gen_expansion(accodati, length-1)
    else:
        return list(it.chain.from_iterable([gen_expansion(s, length) for s in inp]))