擅长:python、mysql、java
<p>似乎您正在尝试获取<code>[]</code>括号内的数据。在</p>
<pre><code>>>> import re
>>> s = """Received: from smtprelay.b.mail.com (smtprelay0225.b.mail.com. [11.11.11.11])
... by mx.google.com with ESMTP id g7si12282480pat.225.2014.07.26.06.53.24
... for <a@gmail.com>;"""
>>> re.search(r'(?<=\[)[^\[\]]*(?=\])', s).group()
'11.11.11.11'
</code></pre>
<p>或者</p>
^{pr2}$