How to use virtualenv in makefile

I like using something that runs only when requirements.txt changes:

This assumes that source files are under project in your project’s root directory and that tests are under project/test. (You should change project to match your actually project name.)

venv: venv/touchfile

venv/touchfile: requirements.txt
    test -d venv || virtualenv venv
    . venv/bin/activate; pip install -Ur requirements.txt
    touch venv/touchfile

test: venv
    . venv/bin/activate; nosetests project/test

clean:
    rm -rf venv
    find -iname "*.pyc" -delete

• Run make to install packages in requirements.txt.
• Run make test to run your tests (you can update this command if your tests are somewhere else).
• run make clean to delete all artifacts.