Commands in the python interpreter are being repeated
<p>I'm new to python and I'm working on a algorithm for calculating uncertainties. The code already existed and I just want to expand it to accept distribution and effective degrees of freedom. However, it seems that every time I try to partial derivate a trig. function a weird thing happens. For ex:</p>

<pre><code>x = ufloat((12,0.0001,9,'sqrt(3)'))
print sin(x)
</code></pre>

<p>If I run this on interpreter the code actually prints <code>sin(x)</code> but the program doesn't stop there. It goes back to definition of the variable <code>x</code> and repeats all the process, generating an error on printing <code>sin(x)</code>. Also, it only prints <code>sin(x)</code> if I setup a break point and do the code step by step.</p>

<p>Is it some feature of python for tracking errors?</p>

<hr>

<p>Tried to use pdb.set_trace() but once i insert the trignometric function i all goes well. No errors. I think because the pdb stops the program from processing the previous commands.</p>

<p>Pastebin with source code:
<a href="http://pastebin.com/PmKkTGCG" rel="nofollow">http://pastebin.com/PmKkTGCG</a></p>
