At some stage of your project you will need to check which ones of your python dependencies needs to be upgraded. You definitely want to have a tight control over which packages you are upgrading in order to identify issues.
In order to accomplish this easily, you can use PIP-Tools.
PIP-Tools is brought to you by Vincent Driessen, who is also behind the famous gitflow :)
pip-tools is pip-review + pip-dump
Check it out here : https://github.com/nvie/pip-tools
pip-review => you check available packages updates.
Feeling lucky, go ahead and upgrade them all : pip-review --auto
pip-dump => you will dump the installed packages to your requirements.txt