Version and Virtual Environment
Python Version Management & Virtual Environments
Package Management
Python package dependency management - pip freeze - requirements.txt and constraints.txt
TL;DR
Keep the list of immediate dependencies in requirements.txt without declaring version numbers.
Keep the output of pip freeze with the specific version numbers in constraints.txt.
Adding new packages
As we need new python packages add their names to the requirements.txt file without any restriction and run
1 | pip install -r requirements.txt -c constraints.txt |
Verify that the new package works as needed. (Run your own tests). Then run
1 | pip freeze > constraints.txt |
Then commit both requirements.txt and constraints.txt to your version control system.
Fresh installations
Later, any time you want to install packages to a fresh installation use
1 | pip install -r requirements.txt -c constraints.txt |
Require specific version of a package
If your application requires a specific version of a package add that information to the requirements.txt file.
1 | package-name==SPECIFIC_VERSION |
Upgrade a package
If later you need to upgrade one of your immediate dependencies because you need some feature that only in a newer version exist then add this information as a minimum requirement to the requirements.txt file: package>=SOME_VERSION
Removing required packages
We can simply remove the package from the requirements.txt file. The fact that it and its dependencies are listed in the constraints.txt file does not matter. They won’t be installed. The only problem is that now we might have some lines in the constraints.txt file that are not relevant any more and that might impact a later installation. If you do the regular maintenance as described below then this will be cleaned up the next time you do it.
Regular maintenance
You can do all the upgrades all at once, or you can cherry-pick.
For the former run:
1 | pip install --upgrade -r requirements.txt |
That will try to upgrade all of your dependencies to the latest.
You can upgrade a specific package:
1 | pip install --upgrade PACKAGE |
You can also remove some or all of the entries from the constraints.txt file and then run:
1 | pip install --upgrade -r requirements.txt -c constraints.txt |
