Python 正则表达式 findall 交替行为

Question

我正在使用 Python 2.7.6。我无法理解 re.findall 的以下结果：

>>> re.findall('\d|\(\d,\d\)', '(6,7)')
['(6,7)']

我预计以上为 return ['6', '7']，因为根据 documentation:

'|'

A|B, where A and B can be arbitrary REs, creates a regular expression that will match either A or B. An arbitrary number of REs can be separated by the '|' in this way. This can be used inside groups (see below) as well. As the target string is scanned, REs separated by '|' are tried from left to right. When one pattern completely matches, that branch is accepted. This means that once A matches, B will not be tested further, even if it would produce a longer overall match. In other words, the '|' operator is never greedy. To match a literal '|', use \|, or enclose it inside a character class, as in [|].

感谢您的帮助

Answer 1

如文档中所述：

This means that once A matches, B will not be tested further, even if it would produce a longer overall match.

所以在这种情况下正则表达式引擎不匹配 \d 因为你的字符串用 ( 而不是 \d 所以它将匹配第二种情况 \(\d,\d\).但是，如果您的字符串以 \d 开头，它将匹配 \d :

>>> re.findall('\d|\d,\d\)', '6,7)')
['6', '7']