Yosemite and python matplotlib issue

Question

Python codes were working well until I upgraded to Yosemite. Any idea please? Here is the error:

Traceback (most recent call last):
  File "/Users/will/Downloads/legend_demo4.py", line 1, in <module>
    import matplotlib.pyplot as plt
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/pyplot.py", line 26, in <module>
    from matplotlib.figure import Figure, figaspect
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/figure.py", line 32, in <module>
    from matplotlib.image import FigureImage
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/image.py", line 22, in <module>
    import matplotlib._png as _png
ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/_png.so, 2): Library not loaded: /usr/X11/lib/libpng12.0.dylib
  Referenced from: /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/_png.so
  Reason: image not found

Answer 1

I had the same problem. I fixed that by un- (via: easy_install -m matplotlib) and reinstalling (via: python setup.py build; python setup.py install) the matplotlib from the sources and afterwards install the wheels package (via: pip install packagename.whl).