Python Code Checker
Find Python bugs: mutable default arguments, bare except, is with literals, eval, shadowed built-ins and more. Free and private: runs in your browser.
Paste Python code to catch bug-prone patterns that PEP 8 style checks miss.
Runs entirely in your browser. Nothing you paste is uploaded or stored.
Use cases
- Check a function before opening a pull request.
- Explain a review comment with numbers instead of opinions.
- Find the riskiest code to refactor first.
Frequently asked questions
What is the mutable default argument bug?
def f(items=[]) creates the list once, so every call shares it. Use items=None and create the list inside the function.
Is the Python Code Checker free?
Yes. It is free with no sign-up, and it runs entirely in your browser, so your input is never uploaded or stored.
How accurate is a browser-based code check?
It uses fast heuristics on the snippet you paste, so it is great for quick feedback. For whole repositories, cross-file analysis and history, run a full CodeInspector scan.
Related tools
Checking one snippet is a start. Scan your whole repository for free with CodeInspector.