来自：http://www.cnblogs.com/luckjun/p/4958338.html
pip:
python
import pip
from subprocess import call
for dist in pip.get_installed_distributions():
call("sudo pip install --upgrade "+dist.project_name, shell=True)
pip3:
python3
import pip
from subprocess import call
for dist in pip.get_installed_distributions():
call("sudo pip3 install --upgrade "+dist.project_name, shell=True)
