pexpect 示例程序：python.py

#!/usr/bin/env python

"""This starts the python interpreter; captures the startup message; then gives
the user interactive control over the session. Why? For fun... """

# Don't do this unless you like being John Malkovich
# c = pexpect.spawn ('/usr/bin/env python ./python.py')

import pexpect
c = pexpect.spawn ('/usr/bin/env python')
c.expect ('>>>')
print 'And now for something completely different...'
f = lambda s:s and f(s[1:])+s[0] # Makes a function to reverse a string.
print f(c.before)
print 'Yes, it\'s python, but it\'s backwards.'
print
print "Escape character is '^]'."
print c.after,
c.interact()
c.kill(1)
print 'is alive:', c.isalive()

需要注意的地方：

f = lambda s:s and f(s[1:])+s[0] # Makes a function to reverse a string.

lambda是用来定义简短函数的一种办法，注意这里还使用了递归，巧妙地利用and来判断递归的结束。

本程序执行过程中可能会报I／O错误。