无法在cygwin中导入numpy

我已经使用cygwin安装程序安装了numpy，并且显示为已成功安装。但是我无法将其导入程序中。

Traceback (most recent call last):
File "pythonpath.py", line 1, in <module>
import numpy
File "/usr/lib/python2.7/site-packages/numpy/__init__.py", line 170, in <module>
from . import add_newdocs
File "/usr/lib/python2.7/site-packages/numpy/add_newdocs.py", line 13, in <module>
from numpy.lib import add_newdoc
File "/usr/lib/python2.7/site-packages/numpy/lib/__init__.py", line 18, in <module>
from .polynomial import *
File "/usr/lib/python2.7/site-packages/numpy/lib/polynomial.py", line 19, in <module>
from numpy.linalg import eigvals, lstsq, inv
File "/usr/lib/python2.7/site-packages/numpy/linalg/__init__.py", line 51, in <module>
from .linalg import *
File "/usr/lib/python2.7/site-packages/numpy/linalg/linalg.py", line 29, in <module>
from numpy.linalg import lapack_lite, _umath_linalg
ImportError: No such file or directory

我查了一下，发现这两个lapack_lite.dll和_umath_linalg.dll可下/lib/python2.7/site-packages/numpy/linalg

当我尝试重新安装numpy时，出现以下消息：

$ pip install numpy
Requirement already satisfied: numpy in /usr/lib/python2.7/site-packages

该软件包也是最新的。

 $ pip install numpy --upgrade
 Requirement already up-to-date: numpy in /usr/lib/python2.7/site-packages

如何在程序中导入numpy？