054-flask/docs/wiki/Lecture-5-First-Class-Functions.md

Lecture 5: Functions as first-class objects

English · Dansk · Bahasa Malaysia

What the lecture covers

In Python a function is an object like an integer or a string: it can be passed as an argument, defined inside another function and returned from it. The calculate function takes two numbers and another function (add or subtract) and applies it. A nested function can be called by its parent but not from outside. A function can return a nested function, and the caller stores it in a variable and calls it later. The tool Python Tutor shows the steps visually.

What we gained

• The idea behind decorators: a function that receives a function and returns a function.
• The scope rule for nested functions, confirmed by a test that the nested name is not reachable from outside.
• The assignment's names (add, subtract, calculate) in code that other course participants can read and run.

In this repository

Code: src/flask_day_54/domain/first_class_functions.py. Tests: tests/unit/test_first_class_functions.py.