6.6 Function Stubs

Incremental development and function stubs

• Programs are typically written using incremental development
• To assist with the incremental development process, programmers commonly introduce function stubs, which are function definitions whose statements haven't been written yet.
• The benefit of a function stub is that the high-level behavior of the program can be captured before diving into details of each function
• Capturing high-level behavior first may lead to better-organized code, reduced development time, and even to code with fewer bugs.
• A programmer writing a function stub should consider whether or not calling the unwritten function is a valid operation.
  • One approach is to use the pass keyword, which performs no operation except to act as a placeholder for a required statement.

The function steps_to_calories() above contains a single pass statement because at least one statement is required in any user-defined function

Another useful approach is to print a message when a function stub is called, thus alerting the user to the missing function statements.

• Good practice is for a stub to return -1 for a function that will have a return value.
• In some cases, a programmer may want a program to stop executing if an unfinished function is called
  • Ex: A program that requires user input should not execute if the user-defined function that gets input is not completed.
  • In such cases, a NotImplementedError can be generated with the statement raise NotImplementedError
  • The NotImplementedError indicates that the function is not implemented and causes the program to stop execution