All possible ways to interleave two strings

Question

I am trying to generate all possible ways to interleave any two arbitrary strings in Python.

For example: If the two strings are \'ab\' and \'cd\'

Answer 1

You only need to compare the index of a to b and c to d then filter out those elements where index of a is greater than index of b and index of c is greater than index of d.

def interleave(s, t):
    mystring = s + t
    return [el for el in [''.join(item) for item in permutations(mystring) if  item.index('a') < item.index('b') and item.index('c') < item.index('d')]]

Demo:

>>> from itertools import permutations
>>> s = 'ab'
>>> t = 'cd'
>>> [el for  el in [''.join(item) for item in permutations(s+t) if item.index('a') < item.index('b') and item.index('c') < item.index('d')]]
['abcd', 'acbd', 'acdb', 'cabd', 'cadb', 'cdab']