# error: command 'gcc' failed with exit code 1
  ...
  building 'mypkg._ext' extension
  gcc -pthread -B /opt/conda/compiler_compat -Wl,--sysroot=/ -Wsign-compare ...
  mypkg/_ext.c:10:10: fatal error: Python.h: No such file or directory

- **ID:** `python/setuptools-command-error-build-ext`
- **Domain:** python
- **Category:** install_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The Python development headers (Python.h) are not installed, so setuptools cannot compile a C extension during the build step.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (97% success)
   ```
   On Debian/Ubuntu: sudo apt-get install python3-dev; on RHEL: sudo dnf install python3-devel; then retry pip install.
   ```
2. **** (90% success)
   ```
   Run pip install --only-binary=:all: mypkg to force wheel usage.
   ```

## Dead Ends

- **** — The failure is a missing system header, not an outdated setuptools. (92% fail)
- **** — Does not provide Python.h. (90% fail)
- **** — The header does not exist at that path without installing python3-dev. (85% fail)