python type_error ai_generated true

TypeError: argument of type 'NoneType' is not iterable

ID: python/fastapi-typeerror-argument-of-type-is-not-iterable

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2025-06-18First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

Trying to iterate over a variable that is None, often from a query parameter or dependency that returns None.

generic

中文

尝试迭代一个为None的变量，通常来自返回None的查询参数或依赖项。

Workarounds

  1. 95% success Check for None before iterating 
    if items is not None:
    for item in items: pass
  2. 90% success Provide default empty list 
    items = request.query_params.get('items', [])

Dead Ends

Common approaches that don't work:

  1. Assuming all parameters are always provided 70% fail

    Optional parameters can be None if not provided.

  2. Using for loop without checking None 90% fail

    None is not iterable.