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POWhy does a memmap need a filename when I try to reshape a numpy array?
 

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  1. POWhy does a memmap need a filename when I try to reshape a numpy array?
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    <p>I am getting a stacktrace that I find difficult to understand:</p> <pre><code>screwed_up_code.py in atleast_4d(arr) 28 def atleast_4d(arr): 29 stshape = arr.shape 30 while len(stshape)&lt;4: stshape+=(1,) 31 print arr.shape, stshape ---&gt; 32 return arr.reshape(stshape) /usr/lib/python2.7/dist-packages/numpy/core/memmap.pyc in __array_finalize__(self, obj) 255 if hasattr(obj, '_mmap'): 256 self._mmap = obj._mmap --&gt; 257 self.filename = obj.filename 258 self.offset = obj.offset 259 self.mode = obj.mode AttributeError: 'memmap' object has no attribute 'filename' </code></pre> <p>In case you wonder <code>arr.shape = (192, 384, 6)</code> and <code>stshape = (192, 384, 6, 1)</code></p> <hr> <p><strong>UPDATE</strong></p> <p>As suggested by NPE , I looked into <a href="http://projects.scipy.org/numpy/ticket/1809" rel="nofollow">the bug report of a similar sounding AttributeError</a>. A poster there blamed it on attributes getting lost due to pickling of ndarrays. I am indeed pickling arrays and when re-vitalize the loaded arrays like so:</p> <pre><code>newarr = numpy.ndarray(pickled_array) pickled_array = newarr # use the recreated instead of the pickled arr </code></pre> <p>I get warnings instead of Exceptions and my code runs:</p> <pre><code>Exception AttributeError: AttributeError("'NoneType' object has no attribute 'tell'",) in ignored Exception AttributeError: AttributeError("'NoneType' object has no attribute 'tell'",) in ignored Exception AttributeError: AttributeError("'NoneType' object has no attribute 'tell'",) in &lt;bound method memmap.__del__ of memmap([ 85389.2734375, 125935.75 , 173624.09375 , 272958.78125 , 305687.65625 , 433026.3125 ], dtype=float32)&gt; ignored </code></pre> <p>I am happy enough that my code runs and will leave it at that for the moment.</p>
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      1. POWhy does a memmap need a filename when I try to reshape a numpy array?
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    1. COIt would really help us to help you if you included an SSCCE (http://sscce.org/)
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    2. COI know - I wish I could. The problem with all the SSCCE's that I am trying is that they actually work and don't produce this problem. You can see that ```atleast_4d``` is a very benign little function. I am handing in a numpy array of shape (192, 384, 6). When I give it a newly created array of the same size, it doesn't happen. Somehow, my code prepares the array in a way such that it blows up inside ```atleast_4d```.
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      1. POWhy does a memmap need a filename when I try to reshape a numpy array?
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    3. COSounds like this is probably fixed in current numpy. (though that is probably 1.7.x)
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