If you have common code that you want to share across multiple projects, it may be worth thinking about storing this code in a physically separate project, which is then imported as a dependency into your other projects. This is easily achieved if you host your common code project in github or bitbucket, where you can use pip to install it in any other project. This approach not only helps you to easily share common code across multiple projects, but it also helps protect you from inadvertently creating bad dependencies (i.e. those directed from your common code to your non common code).
The link below provides a good introduction to using pip and virtualenv to manage dependencies, definitely worth a read if you and your team are fairly new to working with python as this is a very common toolchain used for just this kind of problem:
http://dabapps.com/blog/introduction-to-pip-and-virtualenv-python/
And the link below shows you how to pull in dependencies from github using pip:
How to use Python Pip install software, to pull packages from Github?