Source: 📖 Django for Professionals ch2 p33
Installing new software packages within docker and rebuilding the image will prevent Pipfile.lock conflicts.
The automatic generation of the Pipfile.lock file depends heavily on the OS being used. The entire OS that an app runs on can be specified within Docker, so it makes sense to install new packages there where the lock file will be created in compliance with the Docker OS, where the app will always run.
If you install packages to your local computer, which has a different OS to your Docker host, the resulting Pipfile.lock will also be different. This can cause problems when the volumes mount automatically syncs local changes to your Docker filesystem and overwrites the Docker version with the newer local version — the Docker container will be trying to run an incorrect Pipfile.lock file.
After installing a new package, you'll always need to rebuild the image to force
Docker to start a new build with the updated Pipfile and Pipfile.lock.