我用以下方法安装pip：

$ sudo apt-get install python-setuptools, python-pip

但是当我尝试使用pip安装某些东西时出现此错误

sudo pip install Flask
Traceback (most recent call last):
File "/usr/local/bin/pip", line 9, in <module>
  load_entry_point('pip==1.3.1', 'console_scripts', 'pip')()
File "/usr/local/lib/python2.7/dist-packages/pkg_resources.py", line 378, in    load_entry_point
  return get_distribution(dist).load_entry_point(group, name)
File "/usr/local/lib/python2.7/dist-packages/pkg_resources.py", line 2565, in load_entry_point
  raise ImportError("Entry point %r not found" % ((group,name),))
ImportError: Entry point ('console_scripts', 'pip') not found

为什么？？谢谢。