If you have pip install and you want to see what packages have been installed with your installer tools you can simply call this:
pip freeze
It will also include version numbers for the installed packages.
Update
pip has been updated to also produce the same output as pip freeze by calling:
pip list
Note
The output from pip list is formatted differently, so if you have some shell script that parses the output (maybe to grab the version number) of freeze and want to change your script to call list, you’ll need to change your parsing code.