String Replacement Combinations

So I have a string '1xxx1' and I want to replace a certain number (maybe all maybe none) of x's with a character, let's say '5'. I want all possible combinations (...maybe permutat

Solution 1:

How about:

from itertools import product

deffiller(word, from_char, to_char):
    options = [(c,) if c != from_char else (from_char, to_char) for c in word]
    return (''.join(o) for o in product(*options))

which gives

>>> filler("1xxx1", "x", "5")
<generator object <genexpr> at 0x8fa798c>
>>> list(filler("1xxx1", "x", "5"))
['1xxx1', '1xx51', '1x5x1', '1x551', '15xx1', '15x51', '155x1', '15551']

(Note that you seem to be missing 15x51.) Basically, first we make a list of every possible target for each letter in the source word:

>>> word = '1xxx1'>>> from_char = 'x'>>> to_char = '5'>>> [(c,) if c != from_char else (from_char, to_char) for c in word]
[('1',), ('x', '5'), ('x', '5'), ('x', '5'), ('1',)]

And then we use itertools.product to get the Cartesian product of these possibilities and join the results together.

For bonus points, modify to accept a dictionary of replacements. :^)