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Lesson 39: Functions
Level 5, Python Thinks and Repeats. Write a recipe once with def, use it again and again. The new word: function. It follows lesson 38, Lists. Next comes lesson 40, Import a toolbox (random).
What the lesson explains
Recipe cards. def writes a function. Its name runs it.
def, then use it. name in the brackets is filled in each time. On the card: def greet(name):
What you do first
Call it again. Greet Mia too. The editor opens with: def greet(name): / print("Hello, " + name + "!") / / greet("Ada"). One way to write it: def greet(name): / print("Hello, " + name + "!") / / greet("Ada") / greet("Mia"). It prints: Hello, Ada! / Hello, Mia!.
The code on the screen
def, then use it. The editor shows 5 lines: def greet(name): / print("Hello, " + name + "!") / / greet("Ada") / greet("Sam"). Run it, and it prints "Hello, Ada!", "Hello, Sam!".
What you practise
Try it, "Call it again": Greet Mia too. The editor opens with: def greet(name): / print("Hello, " + name + "!") / / greet("Ada"). One way to write it: def greet(name): / print("Hello, " + name + "!") / / greet("Ada") / greet("Mia"). It prints: Hello, Ada! / Hello, Mia!.
Try it, "Hand an answer back": Finish double so it prints 14. The editor opens with: def double(n): / / / print(double(7)). One way to write it: def double(n): / return n * 2 / / print(double(7)). It prints: 14.
Challenge, "Your own function": Write square and print square(5). One way to write it: def square(n): / return n * n / / print(square(5)). It prints: 25.
What PlayBuddy and PlayType say
PlayBuddy: "A function is a recipe card. Write it once, use it again and again."
PlayType: "A function can hand an answer back. That is called returning."
Help in every lesson
Everything happens on a pretend computer in your browser, so nothing touches your real files. PlayBuddy and PlayType stand beside the board, cheer you on and say when it is your turn.
A green ring shows where to click the first time. After that you do it on your own, and if you slip twice the ring comes back.
Stars
The lesson has 3 things to do. Up to one slip in ten gives three stars, up to one in four gives two, and finishing always gives at least one. Stars and progress are saved in this browser only; there is no account.
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