python - 如何从 Python 中的一组正则表达式匹配中提取第一个非空匹配？

Question

假设我有一个正则表达式(a)|(b)|(c)|(d)。如果我将它应用于文本 'foobar' 我会得到一个匹配对象

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

如何从这里提取 'b'？或者一般来说，如何从未知数量的组中提取第一个匹配项(动态构建正则表达式时可能发生)？

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