Manage Python virtual environment from your Makefile

I often use Makefiles not just as a build tool but as a handy way to execute sequences of commands. The commands I've found myself executing again and again lately are the ones to manage Python virtual environments:

• Create new venv
• Update pip to the latest version that enables all the cool new features
• Install project requirements
• Delete venv and redo it again to see if everything still works from clean slate

The process is tedious and begs to be automated. And Makefile is a good fit because in addition to basic scripting capabilities it offers proper dependency handling that simplifies the task quite a bit.

The outcome of my attempts at such automation is Makefile.venv - a Makefile that seamlessly handles all virtual environment routines without ever needing to be explicitly invoked. Instead, you write make targets that depend on venv and refer to all executables in virtual environment via $(VENV)/executable, e.g. $(VENV)/python or $(VENV)/pip.

Using Makefile.venv is easy:

.PHONY: test
test: venv
    $(VENV)/python -m unittest

include Makefile.venv  # All the magic happens here

Despite its apparent simplicity this Makefile will do very much when invoked (watch a screencast):

• A virtual environment will be created in current directory
• Pip will be automatically updated to the latest version
• Project requirements will be installed (both requirements.txt and setup.py are supported)
• If setup.py is present, the project will be installed in development mode into venv (pip install -e) - all changes to the source code will immediately affect the package in virtual environment.

All these steps will be repeated in case requirements.txt or setup.py is modified. That means you'll never have to worry about syncing venv with its description. Add new dependency to setup.py and consider it installed, because there is no way it'll be forgotten the next time you invoke make.

If you'll need to debug something interactively, there are make python and make ipython for REPL and make bash (or shell or zsh) for shell, but I rarely use those. Most of the time running make with my targets for executing the entry point or running unit tests is enough. In fact, I've noticed that after introducing Makefile.venv into my workflow I've completely stopped activating virtual environments manually.

I encourage you to try Makefile.venv and hope you'll find this approach useful. If you have some comments or would like to point out the faults of using Makefiles for venv, please shoot me an e-mail or create an issue at GitHub project's page.

PS: Makefile.venv was inspired by this StackOverflow thread and by this blog post from the authors of Bottle.py