Running wexpect on windows
===

I have installed wexpect on windows7, now when i am trying to run any command, i am getting below error. I am using MKS toolkit, so ls is a valid command. 

    >>> import pexpect
    >>> pexpect.run('ls ')
    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "C:\Python27\lib\site-packages\winpexpect-1.5-py2.7.egg\pexpect.py", line
    219, in run
    child = spawn(command, maxread=2000, logfile=logfile, cwd=cwd, env=env)
    File "C:\Python27\lib\site-packages\winpexpect-1.5-py2.7.egg\pexpect.py", line
    429, in __init__
    self._spawn (command, args)
    File "C:\Python27\lib\site-packages\winpexpect-1.5-py2.7.egg\pexpect.py", line
    516, in _spawn
    raise ExceptionPexpect ('The command was not found or was not executable: %s
    .' % self.command)
    pexpect.ExceptionPexpect: The command was not found or was not executable: ls.

Can some one please help