tell pip to install the dependencies of packages listed in a requirement file

Question

Developing a Django web app, I have a list of packages I need to install in a virtualenv. Say:

Django==1.3.1 --extra-index-url=http://dist.pinaxproject.com/dev/ Pinax==0.9b1.dev10 git+git://github.com/pinax/pinax-theme-bootstrap.git@cff4f5bbe9f87f0c67ee9ada9aa8ae82978f9890 # and other packages 

Initially I installed them manually, one by one, along the development. This installed the required dependencies and I finally used pip freeze before deploying the app.

Problem is, as I upgraded some packages, some dependencies are no longer used nor required but they keep being listed by pip freeze.

Now, I'd like to set up a new virtualenv this way:

• put the needed packages (without their dependencies) in a requirement file,
  like manual-requirements.txt
• install them with their dependencies
  pip install -r manual-requirement.txt (← problem, this does not install the dependencies)
• freeze the full virtualenv
  pip freeze -r manual-requirements.txt > full-requirements.txt
  and deploy.

Any way to do this without manually re-installing the packages in a new virtualenv to get their dependencies ? This would be error-prone and I'd like to automate the process of cleaning the virtualenv from no-longer-needed old dependencies.

edit: actually, pip does install dependencies not explicitly listed in the requirement file, even if the documentation tells us that such files are flat. I was wrong about which dependencies i expected to be installed. I'll let this question for anyone in doubt about pip not installing all dependencies.

Answer 1

Simply use:

pip install -r requirements.txt 

This installs all dependencies listed in requirements.txt file.