擅长:python、mysql、java
<p>非正则表达式解决方案:</p>
<pre><code>''.join(['$' + c if c.isalpha() else c for c in str])
</code></pre>
<hr/>
<pre><code>>>> str = 'he12th'
>>> ''.join(['$' + c if c.isalpha() else c for c in str])
'$h$e12$t$h'
</code></pre>