Constraints files are requirements files that only control which version of a requirement is installed, not whether it is installed or not.
In a previous post, I talked about ditching pip freeze because it didn't work well with second-level dependencies (especially cross-platform). I found an even better workflow where I use a requirements.txt and a constraints.txt file together. Check out the code in this commit.
requirements ├── constraints.txt └── requirements.txt
Just add a second flag to pip install.
python3 -m pip install -r requirements.txt -c constraints.txt
Inside requirements.txt are packages blogthedata directly uses.
# requirements.txt black Brotli chromedriver-autoinstaller coverage Django ...
Constraints.txt includes everything in requirements.txt plus sub-dependencies
# constraints.txt black==22.3.0 Brotli==1.0.9 cachetools==5.2.0 certifi==2022.6.15 cffi==1.15.1 ...
When used together, we are instructing pip to install everything in requirements.txt with the constraint that if anything is installed that is listed in constraints.txt, use the pinned version.
Now I can be certain sub-dependencies won't break my app without requiring that the sub-dependencies be installed.
About John Solly
I am a Senior Software Engineer with a focus on geospatial applications, based in the Columbus, OH metropolitan area. This blog is where I delve into the intricacies of GIS (Geographic Information Systems), offering deep dives into different components of the geospatial technology stack. For those who share a passion for GIS and its applications, you've found a spot to explore and learn.
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