Can you explain the principle of avoiding code duplication in programming?

The principle of avoiding code duplication (DRY — Don't Repeat Yourself) is about not copying or repeating the same code in different parts of the program. This helps to:

• Reduce the number of errors, as fixes need to be made in one place.
• Make maintenance and development of the code easier.
• Make the code more readable and understandable.

For this, functions, methods, classes, modules, and other mechanisms of code reuse are used. For example, if several tests need to verify the same action, it is better to extract it into a separate method and call it, rather than copying the verification code into each test.