How to bring back library functions which have been deleted?
<p>Suppose I do this</p>

<pre><code>import cmath
del cmath
cmath.sqrt(-1)
</code></pre>

<p>I get this</p>

<pre><code>Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in &lt;module&gt;
NameError: name 'cmath' is not defined
</code></pre>

<p>But when I import <code>cmath</code> again, I am able to use <code>sqrt</code> again</p>

<pre><code>import cmath
cmath.sqrt(-1)
1j
</code></pre>

<p>But when I do the following</p>

<pre><code>import cmath
del cmath.sqrt
cmath.sqrt(-1)
</code></pre>

<p>I get this</p>

<pre><code>Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in &lt;module&gt;
AttributeError: 'module' object has no attribute 'sqrt'
</code></pre>

<p>Even when I import <code>cmath</code> again, I get the same error.</p>

<p>Is it possible to get <code>cmath.sqrt</code> back?</p>

<p>Thanks!</p>
