pip卸载ipython失败

Question

我想卸载ipython，但是

user$ sudo pip uninstall ipython
Not uninstalling ipython at /usr/lib/python2.7/dist-packages, owned by OS

以及

root# pip uninstall ipython
Not uninstalling ipython at /usr/lib/python2.7/dist-packages, owned by OS

为什么我不能阻止伊普顿？

我的ipython是：

user$ ipython
Python 2.7.9 (default, Apr  2 2015, 15:33:21) 
Type "copyright", "credits" or "license" for more information.

IPython 2.3.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: 

在成功升级ipython之后，ipython的版本仍然是2.3.0。 我的操作系统是Ubuntu 15.04 我该怎么办才能解决它。