python 导入模块出错

>>> import matplotlib.pyplot as plt


Traceback (most recent call last):
  File "", line 1, in
    import matplotlib.pyplot as plt
  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 29, in
    from matplotlib.figure import Figure, figaspect
  File "C:\Python27\lib\site-packages\matplotlib\figure.py", line 36, in
    from matplotlib.axes import Axes, SubplotBase, subplot_class_factory
  File "C:\Python27\lib\site-packages\matplotlib\axes\__init__.py", line 4, in
    from ._subplots import *
  File "C:\Python27\lib\site-packages\matplotlib\axes\_subplots.py", line 10, in
    from matplotlib.axes._axes import Axes
  File "C:\Python27\lib\site-packages\matplotlib\axes\_axes.py", line 14, in
    from matplotlib import unpack_labeled_data
ImportError: cannot import name unpack_labeled_data