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

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

when to run the code, error in Eclipse:

import matplotlib.pyplot as plt

:  No module named 

pyplot.

However, switch to another IDE such as pyScript to run the code, it works well.
I change to another workspace where its path have no spaces. eg.D:\EclipseWorkSpace
create a python project and import the last "xxx.py" file.
run again. it works well!!! problem fixed. It's a eclipse issue.
(original workspace is: D:\Documents and Settings\xixiao\workspace)