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I use the Python distribution. Python 2.7 x64 with Windows 7 SP1 x64 Ultimate.

After a conda update --all, whenever I try to import matplotlib.pyplot I get ImportError: DLL load failed: %1 is not a valid Win32 application.. Why?

Full error stack:

Traceback (most recent call last):
  File "C:\svn\hw4\code\test_con.py", line 1, in <module>
    import matplotlib.pyplot as plt
  File "C:\Anaconda\lib\site-packages\matplotlib\pyplot.py", line 109, in <module>
    _backend_mod, new_figure_manager, draw_if_interactive, _show = pylab_setup()
  File "C:\Anaconda\lib\site-packages\matplotlib\backends\__init__.py", line 32, in pylab_setup
    globals(),locals(),[backend_name],0)
  File "C:\Anaconda\lib\site-packages\matplotlib\backends\backend_qt4agg.py", line 17, in <module>
    from .backend_qt5agg import NavigationToolbar2QTAgg
  File "C:\Anaconda\lib\site-packages\matplotlib\backends\backend_qt5agg.py", line 18, in <module>
    from .backend_qt5 import QtCore
  File "C:\Anaconda\lib\site-packages\matplotlib\backends\backend_qt5.py", line 31, in <module>
    from .qt_compat import QtCore, QtGui, QtWidgets, _getSaveFileName, __version__
  File "C:\Anaconda\lib\site-packages\matplotlib\backends\qt_compat.py", line 91, in <module>
    from PyQt4 import QtCore, QtGui
ImportError: DLL load failed: %1 is not a valid Win32 application.
Franck Dernoncourt
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  • be careful when using `conda update --all`. Often conda packages require a specific version of a shared library, but do not block the upgrade. This leads to silent failures. I would downgrade pyqt again. – cel Oct 31 '15 at 18:49
  • Have you tried reinstalling pyqt, e.g. `conda update -f pyqt `? – ali_m Oct 31 '15 at 21:35
  • @ali_m Thanks, I tried but it didn't fix the issue :/ – Franck Dernoncourt Nov 01 '15 at 05:25
  • After a `conda update -f matplotlib` and `conda update -f numpy` I have a new error...: [import matplotlib._png as _png Import: Error: DLL load failed: The specified module could not be found](http://stackoverflow.com/q/33459574/395857) – Franck Dernoncourt Nov 01 '15 at 05:44

2 Answers2

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I had the same issue after running conda update anaconda. The solution that worked for me was to simply to download the latest windows installer, then uninstall and reinstall.

I suspect this is related to the pathname of your conda environment, as if you do a clean install anaconda now wants to live in C:\Users\yourname\AppData\Local\Continuum\Anaconda2, where previously it was just Anaconda (no 2). I suspect after running the upgrade scripts some things are pointing to the nonexistant (for you) "new" path.

I found that if I explicitly activate a conda environment with activate myenvname before running anything it works fine. Likewise if you you run from the "anaconda prompt" (which activates your default environment for you) it works fine. But to get my default environment to stay active from anywhere like its supposed to I had to reinstall.

Nathan Kiner
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  • Thanks, rolling back to the previous Anaconda version fixed this issue. (I've detailed what I did in my answer, but I suspect that `conda install anaconda` is enough) – Franck Dernoncourt Nov 03 '15 at 22:58
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Here is what worked for me:

  1. Run conda update -f matplotlib (from the Anaconda command prompt)

This gave me a new error:

RuntimeError: module compiled against API version a but this version of numpy is 9
Traceback (most recent call last):
  File "C:\svn\hw4\code\test_con.py", line 1, in <module>
    import matplotlib.pyplot 
  File "C:\Anaconda\lib\site-packages\matplotlib\pyplot.py", line 27, in <module>
    import matplotlib.colorbar
  File "C:\Anaconda\lib\site-packages\matplotlib\colorbar.py", line 32, in <module>
    import matplotlib.artist as martist
  File "C:\Anaconda\lib\site-packages\matplotlib\artist.py", line 12, in <module>
    from .transforms import Bbox, IdentityTransform, TransformedBbox, \
  File "C:\Anaconda\lib\site-packages\matplotlib\transforms.py", line 39, in <module>
    from matplotlib._path import (affine_transform, count_bboxes_overlapping_bbox,
ImportError: numpy.core.multiarray failed to import
  1. Run conda update -f numpy

This gave me a new error:

Traceback (most recent call last):
  File "C:\svn\hw4\code\test_con.py", line 1, in <module>
    import matplotlib.pyplot 
  File "C:\Anaconda\lib\site-packages\matplotlib\pyplot.py", line 27, in <module>
    import matplotlib.colorbar
  File "C:\Anaconda\lib\site-packages\matplotlib\colorbar.py", line 34, in <module>
    import matplotlib.collections as collections
  File "C:\Anaconda\lib\site-packages\matplotlib\collections.py", line 27, in <module>
    import matplotlib.backend_bases as backend_bases
  File "C:\Anaconda\lib\site-packages\matplotlib\backend_bases.py", line 56, in <module>
    import matplotlib.textpath as textpath
  File "C:\Anaconda\lib\site-packages\matplotlib\textpath.py", line 22, in <module>
    from matplotlib.mathtext import MathTextParser
  File "C:\Anaconda\lib\site-packages\matplotlib\mathtext.py", line 63, in <module>
    import matplotlib._png as _png
ImportError: DLL load failed: The specified module could not be found.
  1. Run conda install anaconda. This rolled your system back to a stable anaconda distribtution, and solved the issue. (I guess you could skip steps 1 and 2, but I don't feel like going through it again to confirm…)
Franck Dernoncourt
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