how to update\upgrade a package using pip?

What is the way to update a package using pip? those do not work

    pip update
    pip upgrade

I know this is a simple question but as it is not so easy to find (pip documentation doesn't pop up and the q from stack overflow are relevant but are not exactly about that)

The way is

    sudo pip install [package_name] --upgrade

or in short

    sudo pip install [package_name] -U

sudo will ask to enter your root password to confirm the action.

If you do not have a root password (if you are not the admin) you should probably work with virtualenv and then you should drop the sudo:

    pip install [package_name] --upgrade