By default OS doesn't generate the python bindings (they do ship ruby bindings natively). You'll have to download the source code and compile it yourself asking to generate the python bindings. There is documentation out there, including on this very site and on Github:

• GitHub > Building Additional Language Bindings > Python
• You'll also probably want to read Configuring OpenStudio Build Environments
• Here is the list of questions both tagged python and openstudio on Unmet Hours