pip is the most advanced tool for this: you use it by calling pip install <packagename>
The "old" way to do the same is easy_install:
easy_install <packagename>
If you already have easy_install on your system, it is recommended that you run easy_install pip to switch to pip
Both of these installation packages are from the Python Package Index (pypi) The package that provides the easy_install command is usually called python-setuptools (or something similar)