This is the second post in a series about bridging the gap from beginner programmer to advanced data science practitioner. These aren’t programming concepts – they’re software engineering practices that enable you to build robust, maintainable systems.
How to Fix the “Works On My Machine” Problem in Python
You’ve written some Python code that works perfectly on your laptop. You share it with a colleague, and suddenly nothing runs. Or worse – you come back to your own project from last year, and it’s completely broken. Python has been updated, some packages followed the new version, others didn’t, and your carefully crafted solution is now a pile of import errors.
This isn’t a hypothetical scenario. It’s the daily reality of working with Python without proper environment management.

I’ve seen this play out in painful ways. A colleague once spent hours trying to figure out why a package was running slowly, only to discover that the original implementation used PyPy (a super-fast Python implementation), but nobody had documented this crucial detail. Another project mysteriously failed because one developer used conda’s Python, another used the system Python, and a third had installed vanilla Python from python.org. Same code, three different Python installations, three different sets of problems.
The fundamental issue: Python isn’t just Python. There are different versions (3.10, 3.11, 3.12), different implementations (CPython, PyPy, Jython), and countless package versions that may or may not work together. Without managing these variables explicitly, reproducibility becomes impossible.
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