If I initialize an AxesImage using a np.zeros array and then set the axes data later to a np.memmap array, I get a RuntimeError when matplotlib tries to autoscale the image. The errors continue to fill my console and I'm forced to close the shell. This bug was introduced when I switched from numpy v1.0.3.1 to the trunk v1.0.5.dev4815 The two hacks to get around this are: 1) Setting any array element to something other than zero fixes the error: zdata[0,0] = 1 2) Specify the extent and max/min values when creating the image: imgaxes = pylab.imshow(zdata, extent=(0, data_shape[1], data_shape[0], 0), vmin=0, vmax=1) Unfortunately, due to the way this errors I'm having a difficult time debugging it. I'm hoping someone with in-depth knowledge of masked_arrays will have some insight. Code and output are below. Thanks! Chris ---- script to reproduce the bug ---- import pylab import numpy as np def printinfo(imgaxes): a = imgaxes.get_array() print '\nimgaxes array info:' print 'type', type(a) print 'shape', a.shape print 'dtype', a.dtype print 'has _mmap', hasattr(a, '_mmap') data_type = 'float32' data_shape = (30, 40) zdata = np.zeros(data_shape, dtype=data_type) #zdata[0,0] = 1 # No exception raised if this line is executed imgaxes = pylab.imshow(zdata) printinfo(imgaxes) mmdata = np.memmap('foo.dat', dtype=zdata.dtype, shape=zdata.shape, mode='w+') imgaxes.set_data(mmdata) printinfo(imgaxes) # imgaxes array now has a _mmap pylab.show() ---- version info ---- In [2]: pylab.matplotlib.__version__ Out[2]: '0.91.2' In [4]: numpy.version.version Out[4]: '1.0.5.dev4817' ---- error ---- In [26]: run memmap_reassign.py imgaxes array info: type <class 'numpy.ma.core.MaskedArray'> shape (30, 40) dtype float32 has _mmap False imgaxes array info: type <class 'numpy.ma.core.MaskedArray'> shape (30, 40) dtype float32 has _mmap True Exception exceptions.RuntimeError: 'maximum recursion depth exceeded' in ignored ERROR: An unexpected error occurred while tokenizing input The following traceback may be corrupted or invalid The error message is: ('EOF in multi-line statement', (10, 0)) --------------------------------------------------------------------------- RuntimeError Traceback (most recent call last) /Users/cburns/local/lib/python2.5/site-packages/matplotlib/backends/backend_wx.pyc in _onPaint(self, evt) 1079 self.realize() 1080 # Render to the bitmap -> 1081 self.draw(repaint=False) 1082 # Update the display using a PaintDC 1083 self.gui_repaint(drawDC=wx.PaintDC(self)) /Users/cburns/local/lib/python2.5/site-packages/matplotlib/backends/backend_wxagg.pyc in draw(self, repaint) 59 """ 60 DEBUG_MSG("draw()", 1, self) ---> 61 FigureCanvasAgg.draw(self) 62 63 self.bitmap = _convert_agg_to_wx_bitmap(self.get_renderer(), None) /Users/cburns/local/lib/python2.5/site-packages/matplotlib/backends/backend_agg.pyc in draw(self) 356 357 self.renderer = self.get_renderer() --> 358 self.figure.draw(self.renderer) 359 360 def get_renderer(self): /Users/cburns/local/lib/python2.5/site-packages/matplotlib/figure.pyc in draw(self, renderer) 622 623 # render the axes --> 624 for a in self.axes: a.draw(renderer) 625 626 # render the figure text /Users/cburns/local/lib/python2.5/site-packages/matplotlib/axes.pyc in draw(self, renderer, inframe) 1303 mag = renderer.get_image_magnification() 1304 ims = [(im.make_image(mag),0,0) -> 1305 for im in self.images if im.get_visible()] 1306 1307 /Users/cburns/local/lib/python2.5/site-packages/matplotlib/image.pyc in make_image(self, magnification) 129 im.is_grayscale = False 130 else: --> 131 x = self.to_rgba(self._A, self._alpha) 132 im = _image.fromarray(x, 0) 133 if len(self._A.shape) == 2: /Users/cburns/local/lib/python2.5/site-packages/matplotlib/cm.pyc in to_rgba(self, x, alpha, bytes) 74 x = ma.asarray(x) 75 x = self.norm(x) ---> 76 x = self.cmap(x, alpha=alpha, bytes=bytes) 77 return x 78 /Users/cburns/local/lib/python2.5/site-packages/matplotlib/colors.pyc in __call__(self, X, alpha, bytes) 431 vtype = 'array' 432 xma = ma.asarray(X) --> 433 xa = xma.filled(0) 434 mask_bad = ma.getmask(xma) 435 if xa.dtype.char in npy.typecodes['Float']: /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in filled(self, fill_value) 1542 m = self._mask 1543 if m is nomask or not m.any(): -> 1544 return self._data 1545 # 1546 if fill_value is None: /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in _get_data(self) 1472 1473 """ -> 1474 return self.view(self._baseclass) 1475 _data = property(fget=_get_data) 1476 data = property(fget=_get_data) /Users/cburns/local/lib/python2.5/site-packages/numpy/core/memmap.pyc in __array_finalize__(self, obj) 204 self._mmap = obj._mmap 205 else: --> 206 raise ValueError, 'Cannot create a memmap from object %s'%obj 207 else: 208 self._mmap = None /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in __str__(self) 1614 m = self._mask 1615 if m is nomask: -> 1616 res = self._data 1617 else: 1618 if m.shape == (): /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in _get_data(self) 1472 1473 """ -> 1474 return self.view(self._baseclass) 1475 _data = property(fget=_get_data) 1476 data = property(fget=_get_data) /Users/cburns/local/lib/python2.5/site-packages/numpy/core/memmap.pyc in __array_finalize__(self, obj) 204 self._mmap = obj._mmap 205 else: --> 206 raise ValueError, 'Cannot create a memmap from object %s'%obj 207 else: 208 self._mmap = None /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in __str__(self) 1614 m = self._mask 1615 if m is nomask: -> 1616 res = self._data 1617 else: 1618 if m.shape == (): /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in _get_data(self) 1472 1473 """ -> 1474 return self.view(self._baseclass) 1475 _data = property(fget=_get_data) 1476 data = property(fget=_get_data) /Users/cburns/local/lib/python2.5/site-packages/numpy/core/memmap.pyc in __array_finalize__(self, obj) 204 self._mmap = obj._mmap 205 else: --> 206 raise ValueError, 'Cannot create a memmap from object %s'%obj 207 else: 208 self._mmap = None .... [snip] /Users/cburns/local/lib/python2.5/site-packages/numpy/ma/core.pyc in _get_data(self) 1472 1473 """ -> 1474 return self.view(self._baseclass) 1475 _data = property(fget=_get_data) 1476 data = property(fget=_get_data) RuntimeError: maximum recursion depth exceeded Exception exceptions.AttributeError: "'memmap' object has no attribute '_mmap'" in ignored Exception exceptions.AttributeError: "'memmap' object has no attribute '_mmap'" in ignored [snip] Exception exceptions.AttributeError: "'memmap' object has no attribute '_mmap'" in <bound method memmap.__del__ of memmap([ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])> ignored Exception exceptions.AttributeError: "'memmap' object has no attribute '_mmap'" in <bound method memmap.__del__ of memmap([ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])> ignored [snip]