The Pragmatic Programmer: From Journeyman to Master

Why spend your life developing software unless you care about doing it well?

Instead of excuses, provide options. Don’t say it can’t be done; explain what can be done.

You can’t force change on people. Instead, show them how the future might be and help them participate in creating it.

Involve your users in determining the project’s real quality requirements.

Don’t be swayed by vendors, media hype, or dogma. Analyze information in terms of you and your project.

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

Design components that are self-contained, independent, and have a single, well-defined purpose.

Tracer bullets let you home in on your target by trying things and seeing how close they land.

Design and code in your user’s language.

Use experience you gain as you implement to refine the project time scales.

Use the shell when graphical user interfaces don’t cut it.

Source code control is a time machine for your work—you can go back.

Take a deep breath and THINK! about what could be causing the bug.

Prove your assumptions in the actual environment—with real data and boundary conditions.

Code generators increase your productivity and help avoid duplication.

Use contracts to document and verify that code does no more and no less than it claims to do.

Assertions validate your assumptions. Use them to protect your code from an uncertain world.

Where possible, the routine or object that allocates a resource should be responsible for deallocating it.

Implement technology choices for an application as configuration options, not through integration or engineering

Exploit concurrency in your user’s workflow.

Allow for concurrency, and you’ll design cleaner interfaces with fewer assumptions.

Use blackboards to coordinate disparate facts and agents, while maintaining independence and isolation among participants.

Get a feel for how long things are likely to take before you write code.

Just as you might weed and rearrange a garden, rewrite, rework, and re-architect code when it needs it. Fix the root of the problem.

Test ruthlessly. Don’t make your users find bugs for you.

Requirements rarely lie on the surface. They’re buried deep beneath layers of assumptions, misconceptions, and politics.

Invest in the abstraction, not the implementation. Abstractions can survive the barrage of changes from different implementations and new technologies.

When faced with an impossible problem, identify the real constraints. Ask yourself: “Does it have to be done this way? Does it have to be done at all?”

Don’t fall into the specification spiral—at some point you need to start coding.

Beware of vendor hype, industry dogma, and the aura of the price tag. Judge tools on their merits.

A shell script or batch file will execute the same instructions, in the same order, time after time.

‘Nuff said.

Identify and test significant program states. Just testing lines of code isn’t enough.

Write documents as you would write code: honor the DRY principle, use metadata, MVC, automatic generation, and so on.

Come to understand your users’ expectations, then deliver just that little bit more.

Turn off the autopilot and take control. Constantly critique and appraise your work.

Fix bad designs, wrong decisions, and poor code when you see them.

Don’t get so engrossed in the details that you forget to check what’s happening around you.

Make learning a habit.

There’s no point in having great ideas if you don’t communicate them effectively.

If it’s easy to reuse, people will. Create an environment that supports reuse.

No decision is cast in stone. Instead, consider each as being written in the sand at the beach, and plan for change.

Prototyping is a learning experience. Its value lies not in the code you produce, but in the lessons you learn.

Estimate before you start. You’ll spot potential problems up front.

Plain text won’t become obsolete. It helps leverage your work and simplifies debugging and testing.

The editor should be an extension of your hand; make sure your editor is configurable, extensible, and programmable.

It doesn’t really matter whether the bug is your fault or someone else’s—it is still your problem, and it still needs to be fixed.

It is rare to find a bug in the OS or the compiler, or even a third-party product or library. The bug is most likely in the application.

You spend a large part of each day working with text. Why not have the computer do some of it for you?

Software can’t be perfect. Protect your code and users from the inevitable errors.

A dead program normally does a lot less damage than a crippled one.

Exceptions can suffer from all the readability and maintainability problems of classic spaghetti code. Reserve exceptions for exceptional things.

Avoid coupling by writing “shy” code and applying the Law of Demeter.

Program for the general case, and put the specifics outside the compiled code base.

Design in terms of services—independent, concurrent objects behind well-defined, consistent interfaces.

Gain flexibility at low cost by designing your application in terms of models and views.

Rely only on reliable things. Beware of accidental complexity, and don’t confuse a happy coincidence with a purposeful plan.

Mathematical analysis of algorithms doesn’t tell you everything. Try timing your code in its target environment.

Start thinking about testing before you write a line of code.

Wizards can generate reams of code. Make sure you understand all of it before you incorporate it into your project.

It’s the best way to gain insight into how the system will really be used.

Create and maintain a single source of all the specific terms and vocabulary for a project.

You’ve been building experience all your life. Don’t ignore niggling doubts.

Don’t blindly adopt any technique without putting it into the context of your development practices and capabilities.

Don’t separate designers from coders, testers from data modelers. Build teams the way you build code.

Tests that run with every build are much more effective than test plans that sit on a shelf.

Introduce bugs on purpose in a separate copy of the source to verify that testing will catch them.

Once a human tester finds a bug, it should be the last time a human tester finds that bug. Automatic tests should check for it from then on.

Documentation created separately from code is less likely to be correct and up to date.

Craftsmen of an earlier age were proud to sign their work. You should be, too.