Python 2.7 matplotlib.pylab导入错误。动态查找

我已经在mac os 10.6.8上更新了matplotlib版本 matplotlib在wxpython应用程序中工作，但在简单命令模式下使用时，我遇到以下与png库和动态查找相关的导入错误

Python 2.7.1 |EPD 7.0-2 (32-bit)| (r271:86832, Dec  3 2010, 15:41:32) 
[GCC 4.0.1 (Apple Inc. build 5488)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> matplotlib.__version__
u'1.4.x'
>>> import matplotlib.pylab
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-    1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/pylab.py", line 230, in <module>
import matplotlib.finance
File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-   1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/finance.py", line 38, in <module>
from matplotlib.collections import LineCollection, PolyCollection
File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/collections.py", line 27, in <module>
import matplotlib.backend_bases as backend_bases
File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/backend_bases.py", line 56, in <module>
import matplotlib.textpath as textpath
File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/textpath.py", line 22, in <module>
from matplotlib.mathtext import MathTextParser
File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/mathtext.py", line 64, in <module>
import matplotlib._png as _png
ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site- packages/matplotlib-1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/_png.so, 2): Symbol not found:  _png_create_info_struct
Referenced from: /Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.5-i386.egg/matplotlib/_png.so
Expected in: dynamic lookup

谢谢大家的帮助

REQUIRED DEPENDENCIES AND EXTENSIONS
             numpy: yes [version 1.9.0.dev-192355e]
               six: yes [using six version 1.4.1]
          dateutil: yes [using dateutil version 1.5]
           tornado: yes [using tornado version 3.2]
         pyparsing: yes [using pyparsing version 2.0.1]
             pycxx: yes [Couldn't import.  Using local copy.]
            libagg: yes [pkg-config information for 'libagg' could not
                    be found. Using local copy.]
          freetype: yes [version 13.2.7]
               png: yes [pkg-config information for 'libpng' could not
                    be found. Using unknown version.]
             qhull: yes [pkg-config information for 'qhull' could not be
                    found. Using local copy.]

OPTIONAL SUBPACKAGES
       sample_data: yes [installing]
          toolkits: yes [installing]
             tests: yes [using nose version 1.0.0 / using mock 1.0.1]

OPTIONAL BACKEND EXTENSIONS
            macosx: yes [installing, darwin]
            qt4agg: no  [PyQt4 not found]
           gtk3agg: no  [Requires pygobject to be installed.]
         gtk3cairo: no  [Requires cairocffi or pycairo to be installed.]
            gtkagg: no  [Requires pygtk]
             tkagg: yes [installing, version 81008]
             wxagg: yes [installing, version 2.8.10.1]
               gtk: no  [Requires pygtk]
               agg: yes [installing]
             cairo: no  [cairocffi or pycairo not found]
         windowing: no  [Microsoft Windows only]

OPTIONAL LATEX DEPENDENCIES
            dvipng: yes [version 1.14]
       ghostscript: yes [version 9.05]
             latex: yes [version 3.1415926]
           pdftops: no