Question

Suppose I have a regular expression (a)|(b)|(c)|(d). If I apply it to text 'foobar' I get a match object

>>> compiled = re.compile('(a)|(b)|(c)|(d)')
>>> compiled.search('foobar').groups()
(None, 'b', None, None)

How do I extract the 'b' from here? Or in general, how do I extract the first match from an unknown number of groups (can happen when the regexp was built dynamically)?

Answer 1

>>> g = (None, 'b', None, None)
>>> next(x for x in g if x is not None)
'b'

>>> g = (None, None, None)
>>> next((x for x in g if x is not None), "default")  # try this with filter :)
'default'

>>> g = (None, None, None)  # so you know what happens, and what you could catch
>>> next(x for x in g if x is not None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration