python runtime_error ai_generated true

RuntimeError: No response returned

ID: python/fastapi-dependency-yield-cleanup

Also available as: JSON · Markdown · 中文
80%Fix Rate
86%Confidence
0Evidence
2024-07-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

In FastAPI, a dependency with yield must be used as a generator; if you forget to yield or return, route fails.

generic

中文

在 FastAPI 中，带有 yield 的依赖必须作为生成器使用；如果忘记 yield 或 return，路由会失败。

Workarounds

  1. 95% success 
    def get_db():
    db = Session()
    try:
        yield db
    finally:
        db.close()

@app.get('/')
def read(db = Depends(get_db)):
    return {'db': db}
  2. 85% success 
    If you need to return, use a regular function without yield.

Dead Ends

Common approaches that don't work:

  1. 90% fail

    FastAPI expects a generator for cleanup; return breaks it.

  2. 70% fail

    Dependency not invoked; no response generated.