{
  "id": "python/pydantic-validation-error-list-type",
  "signature": "pydantic_core._pydantic_core.ValidationError: 1 validation error for Order\nitems\n  Input should be a valid list [type=list_type, input_value='item1,item2', input_type=str]",
  "signature_zh": "pydantic_core._pydantic_core.ValidationError: Order 模型验证错误：items 字段应为列表类型",
  "regex": "pydantic_core\\._pydantic_core\\.ValidationError:\\ 1\\ validation\\ error\\ for\\ Order\\\nitems\\\n\\ \\ Input\\ should\\ be\\ a\\ valid\\ list\\ \\[type=list_type,\\ input_value='item1,item2',\\ input_type=str\\]",
  "domain": "python",
  "category": "type_error",
  "subcategory": null,
  "root_cause": "A comma-separated string was passed to a list-typed field. Pydantic v2 does not split strings into lists automatically.",
  "root_cause_type": "generic",
  "root_cause_zh": "向列表类型字段传入了逗号分隔的字符串。Pydantic v2 不会自动将字符串拆分为列表。",
  "versions": [
    {
      "version": "2.x",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "list() on a string iterates characters, producing ['i','t','e','m','1',',',...].",
      "fail_rate": 0.98,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Security risk and fails because 'item1,item2' is not valid Python syntax for a list.",
      "fail_rate": 0.99,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "",
      "success_rate": 0.96,
      "how": "data['items'] = 'item1,item2'.split(',')",
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "success_rate": 0.94,
      "how": "from pydantic import BaseModel, field_validator\n\nclass Order(BaseModel):\n    items: list[str]\n\n    @field_validator('items', mode='before')\n    @classmethod\n    def split_items(cls, v):\n        if isinstance(v, str):\n            return v.split(',')\n        return v",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": null,
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.88,
  "fix_success_rate": 0.8,
  "resolvable": "true",
  "first_seen": "2024-05-27",
  "last_confirmed": "2025-01-01",
  "last_updated": "2025-01-01",
  "evidence_count": 0,
  "tags": [],
  "locale": "en",
  "aliases": []
}