How to upgrade all installed Pip packages

Pip makes it convenient to install Python programs and modules from PyPI. One problem that I face with it is to upgrade all my installed packages.

• pip help install seems to indicate that the --upgrade will upgrade all installed packages. But in reality it does not.

• One way to solve this is to install the pip-tools package:

$ sudo pip install pip-tools

• This package provides a pip-review tool that can be used to upgrade all installed packages:

$ sudo pip-review --auto --verbose

Tried with: pip-tools 0.3.6, Pip 7.1.0, Python 2.7.6 and Ubuntu 14.04