title: Remove list element without mutation
body: <p>Assume you have a list </p>
  
  <pre><code>&gt;&gt;&gt; m = ['a','b','c']
  </code></pre>
  
  <p>I'd like to make a new list <code>n</code> that has everything except for a given item in <code>m</code> (for example the item <code>'a'</code>).  However, when I use</p>
  
  <pre><code>&gt;&gt;&gt; m.remove('a')
  &gt;&gt;&gt; m
  m = ['b', 'c']
  </code></pre>
  
  <p>the original list is mutated (the value <code>'a'</code> is removed from the original list).  Is there a way to get a new list sans-<code>'a'</code> without mutating the original? So I mean that <code>m</code> should still be <code>[ 'a', 'b', 'c' ]</code>, and I will get a <em>new</em> list, which has to be <code>[ 'b', 'c' ]</code>.</p>