Changing multiple characters by other characters in a string

Question

I\'m trying to manipulate a string.

After extracting all the vowels from a string, I want to replace all the \'v\' with \'b\' and all the \'b\' with \'v\' from the

Answer 1

Python's comprehension and generator expressions are quite powerful.
You can do the vowel removal the same time as you do the join():

>>> volString = {"a", "e", "i", "o", "u", "A", "E", "I", "O", "U"}
>>> s = 'accveioub'
>>> ''.join(c for c in s if c not in volString)
'ccvb'

In fact you do the swap in the join() too but this maybe a little too verbose:

>>> ''.join('v' if c == 'b' else 'b' if c == 'v' else c for c in s if c not in volString)
'ccbv'

You could pull out the swap code into a mapping dict (dict.get(k, v) returns v if k is not in the dictionary):

>>> vbmap = {'b': 'v', 'v': 'b'}
>>> ''.join(vbmap.get(c, c) for c in s if c not in volString)
'ccbv'

The advantage being these solutions avoid all the intermediate string creations.