我在 OS X El Captain 上安装了 matplotlib、anaconda 和 ipython。但即使我尝试了所有可能的方式来设置环境变量，我仍然无法启动 ipython shell --pylab 版本。
以下是错误信息：
ImportError: dlopen(/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/_png.so, 2): Library not loaded: @rpath/libpng16.16.dylib
Referenced from: /Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/_png.so
Reason: Incompatible library version: _png.so requires version 40.0.0 or later, but libpng16.16.dylib provides version 39.0.0
最初，使用pip正常安装matplotlib后，它没有显示出来。然后我从'conda'重新安装了matplotlib，使用命令conda install -c conda-forge matplotlib=1.5.2，现在我不再遇到包未找到的导入错误，但是pylab版本仍然无法正常工作。我尝试升级libpng库，并将其安装在/usr/local中，但还是没用。我不知道如何在/anaconda/site-packages/matplotlib文件夹中升级_png.so。
我还尝试设置libpng.x.dylib库的环境变量，但不知道为什么它不起作用，或者可能我没有正确操作。
以下是完整的屏幕截图，以防有必要：
IPython 5.0.0 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
TerminalIPythonApp WARNING | Eventloop or matplotlib integration failed. Is matplotlib installed?
ImportError Traceback (most recent call last)
/Users/apple/anaconda/lib/python2.7/site-packages/IPython/core/shellapp.pyc in <lambda>(key)
196 shell = self.shell
197 if self.pylab:
--> 198 enable = lambda key: shell.enable_pylab(key, import_all=self.pylab_import_all)
199 key = self.pylab
200 elif self.matplotlib:
/Users/apple/anaconda/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in enable_pylab(self, gui, import_all, welcome_message)
2972 from IPython.core.pylabtools import import_pylab
2973
---> 2974 gui, backend = self.enable_matplotlib(gui)
2975
2976 # We want to prevent the loading of pylab to pollute the user's
/Users/apple/anaconda/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in enable_matplotlib(self, gui)
2933 gui, backend = pt.find_gui_and_backend(self.pylab_gui_select)
2934
--->2935 pt.activate_matplotlib(backend)
2936 pt.configure_inline_support(self, backend)
2937
/Users/apple/anaconda/lib/python2.7/site-packages/IPython/core/pylabtools.pyc in activate_matplotlib(backend)
293 matplotlib.rcParams['backend'] = backend
294
--> 295 import matplotlib.pyplot
296 matplotlib.pyplot.switch_backend(backend)
297
/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/pyplot.py in <module>()
27 from cycler import cycler
28 import matplotlib
--->29 import matplotlib.colorbar
30 from matplotlib import style
31 from matplotlib import _pylab_helpers, interactive
/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/colorbar.py in <module>()
32 import matplotlib.artist as martist
33 import matplotlib.cbook as cbook
---> 34 import matplotlib.collections as collections
35 import matplotlib.colors as colors
36 import matplotlib.contour as contour
/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/collections.py in <module>()
25 import matplotlib.artist as artist
26 from matplotlib.artist import allow_rasterization
---> 27 import matplotlib.backend_bases as backend_bases
28 import matplotlib.path as mpath
29 from matplotlib import _path
/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/backend_bases.py in <module>()
60
61 import matplotlib.tight_bbox as tight_bbox
---> 62 import matplotlib.textpath as textpath
63 from matplotlib.path import Path
64 from matplotlib.cbook import mplDeprecation, warn_deprecated
/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/textpath.py in <module>()
16 from matplotlib.ft2font import FT2Font, KERNING_DEFAULT, LOAD_NO_HINTING
17 from matplotlib.ft2font import LOAD_TARGET_LIGHT
---> 18 from matplotlib.mathtext import MathTextParser
19 import matplotlib.dviread as dviread
20 from matplotlib.font_manager import FontProperties
/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/mathtext.py in <module>()
58
59 import matplotlib.colors as mcolors
---> 60 import matplotlib._png as _png
61 ####################
62
ImportError: dlopen(/Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/_png.so, 2): Library not loaded: @rpath/libpng16.16.dylib
Referenced from: /Users/apple/anaconda/lib/python2.7/site-packages/matplotlib/_png.so
Reason: Incompatible library version: _png.so requires version 40.0.0 or later, but libpng16.16.dylib provides version 39.0.0