20 lines
1.3 KiB
Markdown
20 lines
1.3 KiB
Markdown
# Lecture 5: Functions as first-class objects
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**English** · [Dansk](Lecture-5-First-Class-Functions-da) · [Bahasa Malaysia](Lecture-5-First-Class-Functions-ms)
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## What the lecture covers
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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.
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## What we gained
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- The idea behind decorators: a function that receives a function and returns a function.
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- The scope rule for nested functions, confirmed by a test that the nested name is not reachable from outside.
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- The assignment's names (`add`, `subtract`, `calculate`) in code that other course participants can read and run.
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## In this repository
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Code: `src/flask_day_54/domain/first_class_functions.py`. Tests: `tests/unit/test_first_class_functions.py`.
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