vpython

Let's you run commands in a virtualenv, quickly. vpython does the following:

• finds the requirements.txt file
• if a virtualenv in that directory named "env" doesn't exist:
  • create a Python virtualenv named "env"
  • pip install -r requirements.txt
• Runs env/bin/python with your arguments.

For example, if you have a requirements.txt in ~/code/project, and you're in ~/code/project/tests/dir, then running:

vpython some_test.py

…will run ~/code/project/env/bin/python some_test.py; it'll create the virtualenv if needed and if it does, pip install your requirements.txt.

vipython acts similarly, but starts ipython. (It'll pip install it if needed.)

venv runs arbitrary executables from the virtualenv's bin, so venv nosetests will run your environment's nosetests binary. (Since this works on arbitrary binaries, it can't auto-install PyPI packages.)

Why?

I prefer to not source virtualenvs. Aside from feeling wrong, it messes up Powerline in vim for me. It also prevents you from cd-ing out of the env, and forgetting to call deactivate.