Python in a Nutshell, 4th Edition

Chapter 17. Testing, Debugging, and Optimizing

You’re not finished with a programming task when you’re done writing the code; you’re finished only when the code runs correctly and with acceptable performance. Testing means verifying that code runs correctly by automatically exercising the code under known conditions and checking that the results are as expected. Debugging means discovering causes of incorrect behavior and repairing them (repair is often easy, once you figure out the causes).

Optimizing is often used as an umbrella term for activities meant to ensure acceptable performance. Optimizing breaks down into benchmarking (measuring performance for given tasks to check that it’s within acceptable bounds), profiling (instrumenting the program with extra code to identify performance bottlenecks), and actual optimizing (removing bottlenecks to improve program performance). Clearly, you can’t remove performance bottlenecks until you’ve found out where they are (via profiling), which in turn requires knowing that there are performance problems (via benchmarking).

This chapter covers these subjects in the natural order in which they occur in development: testing first and foremost, debugging next, and optimizing last. Most programmers’ enthusiasm focuses on optimization: testing and debugging are often (wrongly!) perceived as being chores, while optimization is seen as being fun. Were you to read only one section of the chapter, we might suggest that section be “Developing a ...