Virtual environment and python versions for different projects

Question

Let me first outline my desired solution and then elaborate on a specific question how to achieve this state.

I'm soon starting two coding projects in python. I've used python before but never on such big projects. My ideal scenario would be to have a setup where I can run virtual environments and different python version for various project. Some research pointed me to virtualenv / virtualenvwrapper and pyenv . It seems using pyenv-virtualenv or pyenv-virtualenvwrapper there is a nice way to specify the virtualenvironment and python version for a specific project.

Question: Once I've setup a virtualenvironment and python version for a specific project, how easily could I switch in a later stage to a newer python version? Let's say I've started project A with python 3.4 and in one year in the future I would like to move everything to python 3.6. Is this possible in a neat way?

Answer 1

Sure:

$ rm -r my-python-3.4-env
$ virtualenv -p python3.6 my-python-3.6-env
$ source my-python-3.6-env/bin/activate

In other words, each virtual environment is just a folder with the necessary files in it. You "activate" an environment with the source .../activate command (in case of virtualenv) and you leave it just as easily. To switch to a different environment you simply create a new one with a specific Python executable and activate it.

What you want to be careful about is to keep your installation repeatable, meaning if you depend on external modules (which modern projects typically do), you don't want to install each dependency by hand and instead automate that. For instance, you create a setuptools setup.py file which lists your dependencies, and then have it install them into your new environment automatically:

$ source my-python-3.6-env/bin/activate
(my-python-3.6-env) $ python setup.py develop