How to add # in front of multiple line of code?
<p>I see others do this but have no clue how they did.
As title, if I want to add # in front of multiple line of code so that these code wont run, like this</p>

<pre><code>print A
print B
print C
</code></pre>

<p>Then I want them become </p>

<pre><code># print A
# print B
# print C    
</code></pre>

<p>What is the fastest way? </p>