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POPython throws TypeError on issubclass() when issubclass() is never called
 

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  1. POPython throws TypeError on issubclass() when issubclass() is never called
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    <p>I have a piece of code that runs perfectly most of the time, but every once in awhile I get this error in the traceback:</p> <pre><code>File "/path/to/somefile.py", line 272, in somefile sm = -0.5 * (wv[0]**2. / sm2 + numpy.log(2. * numpy.pi * sm2)) TypeError: issubclass() arg 2 must be a class or tuple of classes </code></pre> <p>I know what <code>issubclass()</code> does and understand the error, but I never called it; that line in the code is pure arithmetic, so I don't know why this <code>TypeError</code> is raised in the first place. My only theory is that Numpy is calling it behind the scenes, but then the traceback should show the problematic line in the Numpy source, right? What's going on?</p> <p><strong>Updates:</strong></p> <p><code>wv</code> is an array of floats and <code>sm2</code> is a float scalar. The error is actually thrown by <code>numpy.log</code>, i.e. the (new) line</p> <pre><code>tmp = numpy.log(2. * numpy.pi * sm2) </code></pre> <p>No more information is provided in the error message, though.</p> <p><strong>More updates:</strong></p> <p>My current version of Numpy (from a Python prompt):</p> <pre><code>&gt;&gt;&gt; import numpy &gt;&gt;&gt; numpy.__version__ '1.6.2' </code></pre> <p>I changed the problem line to</p> <pre><code>try: tmp = numpy.log(2. * numpy.pi * sm2) except TypeError: print type(sm2), 2. * numpy.pi * sm2 </code></pre> <p>and got the output</p> <pre><code>&lt;type 'numpy.float64'&gt; 0.0 </code></pre> <p>So it makes sense that there would be <em>some kind</em> of error, but if I do this (at a Python prompt)</p> <pre><code>&gt;&gt;&gt; import numpy &gt;&gt;&gt; numpy.log(0.) </code></pre> <p>I get the error I would expect (and am already handling in the code in question, via the <code>warning</code> module):</p> <pre><code>__main__:1: RuntimeWarning: divide by zero encountered in log -inf </code></pre>
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    1. COYou don't say what each var is, but you can break this statement into small pieces to see where the error happens (probably on `numpy.log`)
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    2. CO@JBernardo is right—but you're almost certainly going to need to know (and tell us) what `sm2` (and possibly `wv`) is in order to solve this problem. So please, do both of his suggestions, not just the second one. (If you don't know what type they are, just print them out right before this line.)
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      1. USabarnert
    3. CO@JBernardo and @abarnert, I've updated with the types of the variables and split the line so that `numpy.log` is executed first, then added on the next line; the error is actually thrown by `numpy.log` but the last traceback line is still in my code, not Numpy's.
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