How can I use a pip requirements file to uninstall as well as install packages?

Question

I have a pip requirements file that changes during development.

Can pip be made to uninstall packages that do not appear in the requirement

Answer 1

Stephen's proposal is a nice idea, but unfortunately it doesn't work if you include only direct requirements in your file, which sounds cleaner to me.

All dependencies will be uninstalled, including even distribute, breaking down pip itself.

Maintaining a clean requirements file while version tracking a virtual environment

Here is how I try to version-track my virtual environment. I try to maintain a minimal requirements.txt, including only the direct requirements, and not even mentioning version constraints where I'm not sure.

But besides, I keep, and include in version tracking (say git), the actual status of my virtualenv in a venv.pip file.

Here is a sample workflow:

---

setup virtualenv workspace, with version tracking:

mkdir /tmp/pip_uninstalling
cd /tmp/pip_uninstalling
virtualenv venv
. venv/bin/activate

initialize version tracking system:

git init
echo venv > .gitignore
pip freeze > venv.pip
git add .gitignore venv.pip
git commit -m "Python project with venv"

install a package with dependencies, include it in requirements file:

echo flask > requirements.txt
pip install -r requirements.txt
pip freeze > venv.pip

Now start building your app, then commit and start a new branch:

vim myapp.py
git commit -am "Simple flask application"
git checkout -b "experiments"

install an extra package:

echo flask-script >> requirements.txt
pip install -r requirements.txt
pip freeze > venv.pip

... play with it, and then come back to earlier version

vim manage.py
git commit -am "Playing with flask-script"
git checkout master

Now uninstall extraneous packages:

pip freeze | grep -v -f venv.pip | xargs pip uninstall -y

I suppose the process can be automated with git hooks, but let's not go off topic.

Of course, it makes sense then to use some package caching system or local repository like pip2pi