Playground

Pick a language and try an idea. Code runs in this tab, and each language keeps its own saved scratch pad in this browser.

Each language keeps its own saved draft.

Scratch pad Python

# Change the text, then press Run. # Your edits are saved in this browser. from collections import Counter text = """the quick brown fox jumps over the lazy dog the quick brown fox is quick""" counts = Counter(text.split()) for word, count in counts.most_common(5): print(f"{word:8} {count}")

Using Python here

The Python runtime loads on first use and is cached by your browser.
input() waits for a response. Type in the input field and press Enter; EOF ends input.
Files you create live in the browser runtime, not on your computer. Threads, subprocesses and raw sockets are unavailable.
Your edits are stored on this device. Copy or download important work before clearing browser data.

Copy a starting point

Open an example and copy it into the scratch pad to try it.

Ask a question

name = input("What is your name? ")
print(f"Hello, {name}!")

Read and write a file

with open("notes.txt", "w") as file:
    file.write("line one\nline two\n")

with open("notes.txt") as file:
    for number, line in enumerate(file, 1):
        print(number, line.rstrip())

Work with JSON

import json

data = {"name": "Ada", "tags": ["python", "maths"]}
text = json.dumps(data, indent=2)

print(text)
print(json.loads(text)["tags"][0])

Time some code

import time

start = time.perf_counter()
total = sum(i * i for i in range(1_000_000))
elapsed = time.perf_counter() - start

print(total)
print(f"{elapsed * 1000:.1f} ms")

Keep learning

Python beginner course →

Scratch pad JavaScript

// Change a duration, then press Run. const sessions = [25, 10]; let total = 0; for (const minutes of sessions) { total += minutes; } console.log("Total: " + total + " minutes");

Using JavaScript here

Use console.log() to show values in the output panel.
Code runs in a worker. It has no webpage document, prompt() dialog or Node.js environment.
Use starting values in your code for input. Stop ends a running program; Reset restores the supplied example for this language.
Your edits are stored on this device. Copy or download important work before clearing browser data.

Copy a starting point

Open an example and copy it into the scratch pad to try it.

Describe an object

const learner = { name: "Ada", minutes: 25 };

console.log(learner.name + " studied for " + learner.minutes + " minutes.");

Write a function

function remaining(planned, completed) {
    return Math.max(0, planned - completed);
}

console.log(remaining(60, 25));

Keep learning

JavaScript beginner course →

Scratch padTypeScript

// Check & run checks the types before executing your code. // Try replacing 25 with "25" to see a type error. const sessions: number[] = [25, 10]; let total: number = 0; for (const minutes of sessions) { total += minutes; } console.log("Total: " + total + " minutes");

Enable JavaScript to edit and type-check this example.

Console output

Using TypeScript here

Check types shows real TypeScript compiler errors with strict checks. The compiler loads on your first check.
Check & run executes only after type checking succeeds. Try a wrong type, read the diagnostic, then fix it.
Code runs in a worker without a webpage document or Node.js. Download .ts saves your current code as a file.
Your edits are stored on this device. Copy or download important work before clearing browser data.

Copy a starting point

Open an example and copy it into the scratch pad to try it.

Describe a typed object

type Learner = {
    name: string;
    minutes: number;
};

const learner: Learner = { name: "Ada", minutes: 25 };

console.log(learner.name);

Type a function

function remaining(planned: number, completed: number): number {
    return Math.max(0, planned - completed);
}

console.log(remaining(60, 25));

Keep learning

TypeScript beginner course →

Scratch pad Java

public class Main { public static void main(String[] args) { // Change a duration, then press Run. int[] sessions = {25, 10}; int total = 0; for (int minutes : sessions) { total += minutes; } System.out.println("Total: " + total + " minutes"); } }

Using Java here

The supplied file is Main.java. Keep the public class Main and main method as the frame for your instructions.
Run compiles and executes a Java 25 subset in your browser. Compiler errors appear in the output panel; a full JDK is not required here.
For Scanner input, fill the standard-input box before Run. Java reads that supplied buffer and then reaches its end; it does not pause for more input.
Your edits are stored on this device. Copy or download important work before clearing browser data.

Copy a starting point

Open an example and copy it into the scratch pad to try it.

Write a method

public class Main {
    public static void main(String[] args) {
        System.out.println(remaining(60, 25));
    }

    static int remaining(int planned, int completed) {
        if (completed >= planned) {
            return 0;
        }

        return planned - completed;
    }
}

Read supplied input

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        if (input.hasNextLine()) {
            String name = input.nextLine();
            System.out.println("Hello, " + name + "!");
        }
    }
}

Keep learning

Java beginner course →