擅长:python、mysql、java
<p>试试这个</p>
<pre><code>import re
s = "Length Le"
re.sub(r'\bLe\b', '<=', s)
</code></pre>
<p>它将匹配正则表达式<code>\bLe\b</code>,并用<code><=</code>替换所有匹配项。这个表达式的意思是<code>"Le" where it's not surrounded by alphanumeric characters</code>。实际上,<code>Le</code>被空格或标点符号包围</p>
<p>关于<a href="https://docs.python.org/2/library/re.html" rel="nofollow">Regex</a>的Python文档值得一读,特别是<code>\b</code>与单词边界匹配</p>