python : matplotlib does not work in Eclipse

I met a problem like this:

[
http://stackoverflow.com/questions/6513753/matplotlib-does-not-work-in-eclipse
import numpy 

import matplotlib.pylab as pylab

import pylab as pl

I get the following error in Eclipse: import matplotlib import pylab as pl from matplotlib.pylab import * ImportError: No module named pylab

Even though the interpreter for Pydev is pointing to the appropriate version of python and matplotlib is installed properly in there (site-packages) it does not work in Eclipse.

]

 

My problem is:

my code:
"
import matplotlib.pyplot as plt
...
"

when to run the code, error in Eclipse: import matplotlib.pyplot as plt:  No module named pyplot.

run again. it works well!!! problem fixed. It's a eclipse issue.
(original workspace is: D:\Documents and Settings\xixiao\workspace)