Python Playground

Real Python, in the page

This playground runs CPython 3.14 compiled to WebAssembly, so the language is exactly the Python you write everywhere else. Modern features are all here: structural pattern matching with match and case, async and await with asyncio.run and asyncio.gather, the walrus operator, dataclasses with slots, f-strings, type hints with the new generic syntax such as def first[T](items: list[T]) -> T and type aliases, and exception groups caught with except*.

Python runs in a background worker, so a slow program never freezes the page, and Stop ends even an infinite loop straight away. Each run starts from a clean slate, with no variables carried over from the last one.

Step through your code

Press Debug and the program runs once while every step is recorded. The editor highlights the line about to run, with the previous line shaded so you can see where execution came from. The call stack lists every active function, and selecting a frame shows its variables with their types and values. Values that changed since the last step are highlighted.

Because the whole run is recorded, you can step backwards as easily as forwards, which makes it easy to find where a value went wrong. Click beside a line number to set a breakpoint, then jump straight to it. For example, debug a recursive factorial(5) and watch five frames build up on the stack, then return 1, 2, 6, 24 and 120 as they unwind.

An editor that helps

The editor colours Python syntax, indents after a colon, matches brackets, folds blocks and supports multiple cursors, search and undo. Autocompletion comes from Jedi, the engine used by many Python editors: type "hello".up and it suggests upper with its signature and documentation, or from collections import de to get defaultdict and deque. Syntax errors are underlined as you type.

Copy and paste work as normal, and there are buttons to copy the code or the output, download your program as a .py file, or open one from disk. Your current code is saved in your browser automatically.

Good for practice

Use it to try out an idea, check how a built-in behaves, or practise for an interview with the Exercises menu, without installing anything. The Examples menu has short programs that show off each modern feature, and every one of them can be run or debugged as a starting point for your own.

Practise with exercises

There are 45 exercises in four groups. Beginner ones cover f-strings, list comprehensions, slicing, tuple unpacking, dicts, enumerate and zip, sets and splitting text. Intermediate ones cover function arguments, special methods, dataclasses, custom exceptions, generators, the collections module, sorting with key, closures, context managers and match statements. Advanced ones cover decorators, the iterator protocol, generics with Protocol, itertools, asyncio.gather, validated properties and exception groups. The Interview group has 20 classic problems in Easy, Medium and Hard, from two sum and valid parentheses to an LRU cache, course scheduling, Dijkstra's shortest paths and edit distance.

Check runs hidden unittest tests against your code and lists every test and subtest as ✓ or ✗ with its message. Interview problems state the complexity to aim for, and 12 of the 20 have a timing test on a large input that rejects an answer of the wrong complexity with a "Too slow" message. The timing check has a wide margin, so it catches the wrong complexity class, not small differences in speed — the exercises are for practice, not a proctored test. Solved exercises get a tick, and your code and progress stay in this browser.