Installation can be done in various ways. The simplest form uses pip or easy_install. Either one will work:
pip install rsa easy_install rsa
Depending on your system you may need to use sudo pip or sudo easy_install.
Installation from source is also quite easy. Download the source and then type:
python setup.py install
or if that doesn't work:
sudo python setup.py install
Python-RSA has very few dependencies. As a matter of fact, to use it you only need Python itself. Loading and saving keys does require an extra module, though: pyasn1. If you used pip or easy_install like described above, you should be ready to go.
In order to start developing on Python-RSA you need a bit more. Use pip to install the development requirements in a virtual environment for Python 2.x:
virtualenv python-rsa-venv-py2x . python-rsa-venv-py2x/bin/activate pip install -r python-rsa/requirements-dev-py2x.txt
or Python 3.x:
virtualenv python-rsa-venv-py3x . python-rsa-venv-py3x/bin/activate pip install -r python-rsa/requirements-dev-py3x.txt
Once these are installed, use Mercurial to get a copy of the source:
hg clone https://bitbucket.org/sybren/python-rsa python setup.py develop