How This Works

Why this matters

You learn Python by writing it, not by reading about it. Every lesson here is a short read followed by hands-on practice. This five-minute tour shows you the tools, so nothing gets in your way later.

The idea

Each lesson page has two halves: the lesson itself, and a workspace where you write code (under the lesson on a small screen). The workspace has:

• The editor. Type Python here. Your code is saved automatically in this browser, so you can close the page and come back.
• Run ▶. Runs your program and shows what it prints under Output. Running is free and safe, so do it as often as you like. Shortcut: Ctrl/⌘ + Enter.
• Check ✔. Runs the lesson’s tests on your code and tells you, in plain language, what passed and what to fix.
• Hints. Three of them, each a little more revealing. Try to get as far as you can before opening the next one.
• Show the solution. Unlocks after a few unsuccessful checks. Looking is fine; just type it out yourself afterwards instead of copying.
• Reset code. Puts the starter code back if you want a fresh start.
• Input box. Some programs ask the person using them to type something. You type it here, before pressing Run.
• Stop ■. Appears while your program runs. If a program never finishes, press it.

Try it

Press Run on the program in the editor. You should see two lines appear under Output. The program is only a few lines long: the first line prints a sentence, and the second prints a message with a number in it.

Your turn

The program has a variable (a named piece of information) called lucky_number, currently set to 0.

1. Change the 0 to 3.
2. Press Run and look at the output.
3. Press Check.

Recap

• Run shows what your program does; Check tests it against the lesson.
• Hints and the solution are there when you are stuck, not as a last resort.
• You cannot break anything. Reset code undoes it all.

Common mistakes

• Changing the code but not pressing Run or Check. Nothing happens until you do.
• Editing the comment instead of the code. Lines that start with # are notes for humans; Python ignores them.