python install_error ai_generated true

ERROR: Some build dependencies for package are missing: 'cython' is required to build the package but is not installed.

ID: python/pip-pep517-requires-build-deps

Also available as: JSON · Markdown · 中文
80%Fix Rate
85%Confidence
0Evidence
2026-01-15First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

The project's build-system.requires lists a build dependency that pip cannot fetch or that is not installed when --no-build-isolation is used.

generic

中文

项目的 build-system.requires 列出了 pip 无法获取的构建依赖，或在使用 --no-build-isolation 时未安装的依赖。

Workarounds

  1. 88% success 
    Install build deps in the host and disable isolation: pip install cython && pip install --no-build-isolation .
  2. 92% success 
    Ensure build-system.requires is correct: [build-system]\nrequires = ["setuptools>=61", "cython>=3.0"]\nbuild-backend = "setuptools.build_meta"
  3. 85% success 
    Check network access to fetch build deps: pip download cython -d /tmp/cython-test

Dead Ends

Common approaches that don't work:

  1. 80% fail

    Installing in the host env does not help when build isolation is enabled; the isolated env still lacks it.

  2. 85% fail

    The build actually needs Cython; removing it causes a different error (missing .c files).

  3. 90% fail

    --no-deps affects runtime deps, not build-time deps.