Using Code Examples in Projects

At some point in a course, most learners want to take a piece of code from the course and bring it into their own work. The question is simple to state: once you have a code example, how do you use it in your own project? This article introduces that question and gives you a careful way to approach it.

Before reading on, ask yourself what you would do with a code example you had just obtained. Would you paste it into your project straight away, or would you first work out what it does? The rest of this article argues for the second approach, and shows what that careful work looks like.

The section this article belongs to is titled Downloading Code Examples, and it sits within the chapter on using code examples in projects. The source material confirms that the section covers downloading code examples. It does not yet describe specific download steps, file locations, or how the examples are structured after download. This article therefore does not list exact download procedures, and it does not claim how examples are stored once they arrive. Anything more specific should be taken from the course materials once they are provided.

Consider a short Python program that calculates the cost of buying several items at the same price. Read it from top to bottom and track what each variable holds after each line runs. The program below is an illustration written for this article; the source describes the idea of the calculation but does not supply this code.

Tracing the example this way shows exactly which values the program depends on. Notice that line 3 does not read a fixed number; it reads whatever price and quantity hold at the moment that line runs. That is the information you need before changing anything.

Suppose your project needs the cost for five items instead of three. The logic stays the same. Only the input value changes, so you change one line and leave the rest alone. Try predicting the result before you read the answer.

A downloaded example should be read and tested with a small input before it is reused in a project. The source names one practical habit: report what you received before you do anything else with it. The script below is an illustration written for this article. It takes a name and a piece of text, then prints how many characters the text contains. Reading its output first lets you confirm that the input is what you expected.

The same idea applies to any downloaded example. Read it from top to bottom, trace which values it depends on, run it with a small input whose result you already know, and only then decide whether it fits your project. Work through the steps in the flowchart below in order.

Once an example has been checked, adapt it to the project. Replace illustrative example values with the values your project actually uses, and adapt one change at a time, running the code after each change to check the result. A project might call the price unit_price, for example. The diagram below compares the original names with the adapted ones. The logic of the calculation is unchanged; only the names and values that belong to the project are different.