How to use this developer tool
- Paste Python code.
- Select a Python version.
- Choose analysis depth.
- Run the checker.
- Fix indentation and syntax issues before style warnings.
#129 · Programming Language Tools Developer Tool
Python Checker
Check Python source for indentation problems, missing colons, bracket and string errors, common anti-patterns, and version-sensitive syntax using browser-based static analysis.
Developer Input
Local browser processingAd space
What this developer tool does
It inspects indentation levels, block headers, declarations, imports, mutable defaults, broad exceptions, built-in shadowing, None comparisons, and selected compatibility features.
Line scan → indentation analysis → bracket/string checks → rule patterns → version checks → issue summary.
The browser cannot import modules or execute Python. Verify final code with python, compileall, Ruff, Flake8, mypy, tests, or your IDE.
Example
Input: a function missing a colon with a list default.
Output: missing-colon and mutable-default warnings with line locations.
Tips for better output
- Use spaces consistently.
- Prefer is None over == None.
- Avoid mutable default arguments.
- Run the target interpreter before deployment.
FAQ
How can I check Python code for indentation errors online?
Paste the code and run the checker. It reports inconsistent indentation and tab/space mixing.
How do I find missing colons in Python code?
The checker flags block-header lines such as def, class, if, for, while, try, except, and with that do not end with a colon.
How can I detect mutable default arguments in Python?
It flags list, dict, and set literals used directly as default parameter values.
How do I check Python version compatibility?
Select a target version. The checker flags selected features such as match/case, walrus expressions, and modern union syntax.
Why does Python code pass a browser checker but fail at runtime?
Static browser analysis cannot import modules, resolve names fully, execute decorators, or reproduce runtime data and environment behavior.
Related developer tools
Python checks
| Module | Purpose |
|---|---|
| Indentation | Levels and tab/space mixing |
| Syntax patterns | Colons, brackets, strings |
| Quality | Mutable defaults and broad except |
| Compatibility | Selected version features |