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PythonStudio
Python 3 in your browser

Online Python compiler
with every step visible.

Python Studio is a free online Python compiler and editor at reads.fyi. Run Python 3 in your browser, supply input, and inspect execution with a step-by-step visualizer. Practice interview problems and test edge cases with Break My Code. No account is needed: drafts stay in this browser, while optional sign-in lets you save programs to your account. Python execution uses Pyodide in your browser, not the application server.

Open the Python editor Running code requires JavaScript. The guides below are readable without it.

Practice Python and test edge cases

Solve 81 interview problems in your browser. Run Tests checks the exercise suite; Break My Code adds targeted edge cases with expected and actual results and failure lessons. No account is required for practice.

Learning guides

01How to find edge cases in Python interview codeFind Python edge cases with Break My Code. Test duplicates, boundaries, and large inputs, compare expected and actual results, and understand failures.Read guide 02How to run Python online without installing itRun your first Python program online for free with Python Studio. Learn how to use the editor, read output, fix errors, and keep browser-saved files safe.Read guide 03How to use input() in an online Python compilerUse Python input() online with prepared standard input. Follow a two-line example, convert strings to numbers, and fix EOFError and ValueError in your code.Read guide 04Visualize Python code and understand recursionUnderstand Python execution with a step-by-step visualizer. Inspect variables, recursive call-stack frames, and source lines in a small factorial example.Read guide 05Async Cache Invalidation: What to Do When a Key Is Invalidated Mid-FetchWhen a cache key is invalidated while its fetch is still in flight, the stale result must not be stored. The version-check fix, with runnable asyncio code.Read guide 06Benchmarking Python Decorator Overhead with timeitMeasure Python decorator overhead with repeated timeit runs, compare wrapped and bare calls, and understand why tiny timing differences need careful checks.Read guide 07How to Write a String (or Encrypted Bytes) to a File or Socket in PythonEncrypted bytes are not text — decoding them as UTF-8 fails. Write bytes with 'wb' and sendall, and use base64 when the ciphertext must travel as text.Read guide 08What to Expect in a Low-Level Design (LLD) RoundAn LLD round is 45–60 minutes: clarify, design the classes, write runnable code. What interviewers score, the questions that repeat, and how to prepare.Read guide

What the workspace does

  • Visualize execution

    Visualize records a run so you can step through each line, watch variables change, and select call-stack frames.

  • Prepared input

    Programs that call input() read one line per call from the Input tab. Output is read-only, not an interactive terminal.

  • Local drafts, optional account saving

    Drafts and prepared input stay in this browser. Sign in and choose Save to reopen a program on other devices, or Download a .py backup.

  • Local completion

    Ctrl+Space or the Suggestions button offers keywords, built-ins, and names from your program. Tab or Enter accepts.

  • Share by link

    Share puts the current code in the URL fragment. Anyone with the link can read it, so keep secrets out.

Questions learners ask

Is this online Python compiler free?

Yes. Running Python, code completion, visualization, interview practice, and rule-based Break My Code tests are free without sign-in. Optional AI-generated cases are separate.

How can I find edge cases in my Python solution?

Open an interview problem, write your solution, and select Break My Code beside Run Tests. It compares your code with a reference on valid edge cases and shows the input, expected result, actual result, and a lesson for failures. Passing a test suite does not prove correctness on every input.

What runs Python behind the scenes?

Python Studio uses Pyodide 0.27.7, which runs CPython as WebAssembly in a browser Web Worker. Your code is not sent to the application server for execution. The first run downloads runtime files from jsDelivr.

Do I need an account or a Python installation?

No account or local Python installation is required. Open Python Studio in a compatible modern browser and run a small Python 3 console program. The initial runtime download requires an internet connection.

How do I enter input for my Python program?

Before running, open the Input tab and put each response on a separate line. Each input() reads the next line as a string. Output is read-only, not an interactive terminal. Convert numeric responses with int() or float().

Where is my code saved, and can it be lost?

Drafts stay in this browser and can be lost if site data is cleared. To keep a program across devices, sign in, choose Save, and wait for 'Saved to your account', or download a .py backup.

Can other people see my saved programs?

Account-saved programs are private. Sharing a code link makes its code readable to anyone with the link, so never include secrets.

Can I install any Python package or run a web server?

This editor does not provide a general pip-install interface or automatic dependency installation. Browser and Pyodide limitations apply to packages, networking, sockets, and operating-system features. Use a local or server environment for a long-running web server.

How does the Python code visualizer work?

Visualize records a bounded run with source-line events, variable snapshots, and call-stack frames. You can step through the recording and inspect recursive callers. Recordings are limited to 500 events; large values can be abbreviated or omitted.

What does code completion support?

Completion suggests Python keywords, built-in functions, and names found in your program. Use Ctrl+Space or the Suggestions button to open it, then Tab or Enter to accept. It is local completion, not an AI assistant or a full type-aware language server.

Python Studio at reads.fyi. Content reviewed .