# error: Cython does not appear to be installed. Use 'pip install Cython' to install it.

- **ID:** `python/setuptools-cython-extension-error`
- **Domain:** python
- **Category:** install_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The setup.py uses Cython extensions but Cython is not installed in the environment.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.8 | active | — | — |
| 3.9 | active | — | — |
| 3.10 | active | — | — |
| 3.11 | active | — | — |
| 3.12 | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   pip install Cython
   ```
2. **** (90% success)
   ```
   [build-system] requires = ['setuptools', 'wheel', 'Cython']
   ```

## Dead Ends

- **** — Global install may not be accessible in virtual environments; also may cause version conflicts. (40% fail)
- **** — Setuptools does not include Cython; it must be explicitly installed. (70% fail)