If you're doing more than one project on your machine then you need to concern yourself with dependencies across projects. In python the old-school way of doing this is to use virtualenv and pip. These tools get the job done, but they may have some caveats you should be aware of.
From python3.4 and up you should not need to install pip. This now comes pre-installed with python. That means that you can install virtualenv in both python versions by running;
python3.6 -m pip install virtualenv python3.7 -m pip install virtualenv
Once it is installed in both python versions you can create a new virtualenv from them by running;
python3.6 -m virtualenv venv36 python3.7 -m virtualenv venv37
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