在ubuntu中导入pyparsing时出错？

Question

获得以下错误

>>> from pyparsing import *
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pyparsing.py", line 9, in <module>
    pp.Literal("+") |
NameError: name 'pp' is not defined

安装python版本2.7.6和ubuntu 14.04