擅长:python、mysql、java
<p>您可以使用<a href="http://docs.python.org/2/library/itertools.html#itertools.takewhile" rel="nofollow">^{<cd1>}</a>:</p>
<blockquote>
<p>Make an iterator that returns elements from the iterable as long as
the <code>predicate</code> is true.</p>
</blockquote>
<p><strong>演示:</strong></p>
<pre><code>>>> from itertools import takewhile
>>> from string import letters,digits
>>> valid_chars = letters + digits + '+/='
>>> text = "gw3AQEFGh8NFgoqDwYsAQALDVFPVltYVkNGXldCRFUbNRk= :jhawrewre: \r\n"
>>> "".join(takewhile(lambda x:x in valid_chars, text))
'gw3AQEFGh8NFgoqDwYsAQALDVFPVltYVkNGXldCRFUbNRk='
</code></pre>