cannot use pexpect of python in cygwin

I was trying to use pexpect in cygwin, but failed. I try to install it like: pexpect-4.1>python ./setup.py install

But when I run the examples inside pexpect-4.1. It outputs:

Traceback (most recent call last):
  File "./examples/uptime.py", line 54, in <module>
    p = pexpect.spawnu('uptime')
AttributeError: module 'pexpect' has no attribute 'spawnu'