Dependencies For Apps

We pin all our dependencies (including dependencies of dependencies) to an exact version in requirements.txt. This makes deployment more deterministic and reproducible.

Sometime we create a requirements.in to list the top level dependencies, with only the known version constraints. This can be used to install the latest versions of all dependencies.

Sometimes a repo has a script to do this.

If an update script doesn't already exist, the basic procedure to add or update a requirement are:

• Update requirements.in or requirements_dev.in as needed.

• Delete the old virtual environment, and start and activate a new one. This is needed to make sure we don't have any extra packages installed.

• Run "pip install -r requirements.in" to install latest requirements.

• Run "pip freeze -r requirements.in > requirements.txt" to create a file listing the exact versions.

• Run "pip install -r requirements_dev.in".

• Run "pip freeze -r requirements_dev.in > requirements_dev.txt".

• Test!