Ignore an element while building list in python
We could create a "subquery".
[r for r in (f(char) for char in string) if r is not None]If you allow all False values (0, False, None, etc.) to be ignored as well, filter could be used:
filter(None, (f(char) for char in string) )# or, using itertools.imap,filter(None, imap(f, string))