Python 或正则表达式和非空结果

Question

我需要找到一个可以采用两种不同形式的子字符串:

>>> test = '348249432'
>>> x = re.findall("([2][0][0-9]{7})|([3][0-9]{8})", test)
>>> x
[('', '348249432')]

我怎样才能让 Python 不返回空字符串，并且只在可以进行匹配的地方给我结果？

Answer 1

findall 返回捕获的组，在 documentation 中说明:

If one or more groups are present in the pattern, return a list of groups; this will be a list of tuples if the pattern has more than one group. Empty matches are included in the result unless they touch the beginning of another match.

你想在一个捕获组中使用交替，我会这样写:

>>> test = '348249432'
>>> re.findall("(20[0-9]{7}|3[0-9]{8})", test)
['348249432']