pip install Works, Production Breaks: Dependency Hell Fix

The Package That Wasn't There

Your CI pipeline is green. pip install ran without errors. The Docker build succeeded. You deploy to production, and suddenly:

ModuleNotFoundError: No module named 'cryptography'

But cryptography is right there in requirements.txt. You can see it in the build logs. It installed successfully. What's happening?

This isn't a random failure. It's the gap between "pip said yes" and "the runtime can actually import it." I've seen this kill three production deployments in one week, each for a different reason.

Photo by Daniil Komov on Pexels

Why pip install Success Means Nothing

When pip install cryptography exits with code 0, it means one thing: pip successfully placed files on disk. It does NOT mean:

• The package can be imported
• Its binary dependencies are present
• The Python version can load it
• Another installed package won't break it at runtime

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