Question

I have a python program which prints out some lists which are created by other python programs in the format of:
[0, [], 0, 1, [], 1]

And I would like to change the 0’s and 1’s to letters, i.e. in the above input, I want to have
[x, [], x, y, [], y] as output

So far my code to do this looks like:

for x in search.Search(s, s.run()):
    if x == 0:
        return x
    elif x == 1
        return y

I know I’m missing something but I’m not too sure what 🙁

Answer 1

Use a list comprehension:

subst = {0: 'x', 1: 'y'}
return [subst.get(v, v) if v else v for v in search.Search(s, s.run()]

By using return you exit the loop early.

The if v else v helps avoid attempting to use the empty lists as keys (which would raise a TypeError; lists are not hashable and thus not allowed as keys). The alternative strategy would be:

from collections import Hashable

subst = {0: 'x', 1: 'y'}
hashable = lambda v: isinstance(v, Hashable)
return [subst.get(v, v) if hashable(v) else v for v in search.Search(s, s.run()]

The subst map is a little easier to extend; but using a function to map the value (as used in Jacob’s answer) could be more readable to you.