The Art of Saying No: Defining Your Python Library's Scope

We’ve all been there, right? You start with a neat little Python script that solves one specific problem. It works beautifully. Then you think, “Hey, I could reuse this!” and decide to turn it into a proper library. Awesome.

But then… the feature creep begins.

“It would be cool if it also did this…” “What if I added support for that obscure edge case?” “My colleague needs it to integrate with this other system…”

Suddenly, your focused little tool starts ballooning. It becomes harder to maintain, harder to test, and frankly, harder for anyone (including future you) to understand what it’s actually supposed to do well.

This is where the Art of Saying No comes in. Defining, and fiercely protecting, the scope of your library is one of the most critical, yet often overlooked, aspects of good library design.

Why Scope Matters (More Than You Think)

• Maintainability: A smaller, focused library is simply easier to manage. Fewer features mean fewer bugs, less complex code, and easier refactoring.
• Usability: Users can quickly grasp what your library does and how to use it. A library that tries to be everything to everyone often ends up being confusing.
• Testability: It’s much easier to write comprehensive tests for a well-defined set of features.
• Clarity of Purpose: A clear scope helps you make better design decisions down the line. Does this new feature really belong here?

Learning to Say “No” (Even to Yourself)

Saying “no” isn’t about being difficult; it’s about discipline. It’s about ensuring your library does one thing (or a small, cohesive set of things) really, really well.

• Define the Core Problem: What specific problem is this library solving? Write it down. Stick it on a post-it note above your monitor. If a feature doesn’t directly serve that core problem, question its inclusion.
• Resist Temptation: Shiny new features are tempting. Ask: Does this belong in this library, or could it be a separate library? Could it be implemented by the user of the library instead?
• Think SRP (Single Responsibility Principle): While often applied to classes or functions, the core idea applies to libraries too. A library should ideally have one primary reason to exist.
• Consider Cohesion vs. Coupling: Aim for high cohesion (features within the library are closely related) and low coupling (the library doesn’t excessively depend on or dictate how other parts of a system must work). Does adding this feature decrease cohesion or increase coupling unnecessarily?

It’s Okay to Have Multiple Libraries!

Sometimes, the right answer is to split functionality. If you find your library naturally diverging into distinct areas, consider breaking it into smaller, more focused packages. This often leads to a healthier ecosystem.

Defining scope isn’t a one-time task. Revisit it as your library evolves. But by mastering the art of saying “no,” you build libraries that are more robust, easier to use, and ultimately, more successful.

What are your battle stories with scope creep? How do you keep your projects focused? Let me know!