[modeller_usage] plot_profiles.py run error

Hi,
   I installed epd-7.1-1-rh5-x86_64 which included pylab in RHEL5.7 64 bit system,When I run 'python plot_profiles.py',I got the error:
"Traceback (most recent call last):
File "plot_profiles.py", line 1, in ?
    import pylab
ImportError: No module named pylab"
--------------------plot_profiles.py--------------------------
import pylab
import modeller

def get_profile(profile_file, seq):
    '''Read `profile_file` into a Python array, and add gaps corresponding to
       the alignment sequence `seq`.'''
    # Read all non-comment and non-blank lines from the file:
    f = file(profile_file)
    vals = []
    for line in f:
        if not line.startswith('#') and len(line) > 10:
            spl = line.split()
            vals.append(float(spl[-1]))
    # Insert gaps into the profile corresponding to those in seq:
    for n, res in enumerate(seq.residues):
        for gap in range(res.get_leading_gaps()):
            vals.insert(n, None)
    # Add a gap at position '0', so that we effectively count from 1:
    vals.insert(0, None)
    return vals

e = modeller.environ()
a = modeller.alignment(e, file='pp2a-pp2a_mult-pp2a_loop.ali')

model = get_profile('pp2a.profile', a['pp2a'])
mult = get_profile('pp2a_mult.profile', a['pp2a_mult'])
loop = get_profile('pp2a_loop.profile', a['pp2a_loop'])

# Plot the template and model profiles in the same plot for comparison:
pylab.figure(1, figsize=(20,12))
pylab.xlabel('Residue index')
pylab.ylabel('DOPE per-residue score')
pylab.plot(model, color='red', linewidth=2, label='Basic Model')
pylab.plot(mult, color='green', linewidth=2, label='Multiple templates')
pylab.plot(loop, color='blue', linewidth=2, label='Loop refinement')
pylab.legend()
pylab.savefig('dope_profile.png', dpi=96)

When I run help(pylab) of enthought in RHEL5.7,it also prompt that follow:
Help on module matplotlib.pylab in matplotlib:

NAME
    matplotlib.pylab

FILE
    /usr/local/epd/lib/python2.7/site-packages/matplotlib/pylab.py

DESCRIPTION
    This is a procedural interface to the matplotlib object-oriented
    plotting library.

    The following plotting commands are provided; the majority have
    MATLAB |reg| [*]_ analogs and similar arguments.

    .. |reg| unicode:: 0xAE

    _Plotting commands
      acorr     - plot the autocorrelation function
      annotate - annotate something in the figure
      arrow     - add an arrow to the axes
      axes      - Create a new axes
      axhline   - draw a horizontal line across axes
: