{
  "id": "python/flask-keyerror-session",
  "signature": "KeyError: 'session'",
  "signature_zh": "KeyError: 'session'",
  "regex": "KeyError:\\ 'session'",
  "domain": "python",
  "category": "data_error",
  "subcategory": null,
  "root_cause": "Trying to access a session key that does not exist, often due to missing secret_key or disabled sessions.",
  "root_cause_type": "generic",
  "root_cause_zh": "尝试访问不存在的会话键，通常是由于缺少 secret_key 或会话被禁用。",
  "versions": [
    {
      "version": "3.x",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "Setting secret_key after first request",
      "why_fails": "Secret key must be set before any session access.",
      "fail_rate": 0.75,
      "condition": "",
      "sources": []
    },
    {
      "action": "Using session without importing",
      "why_fails": "Flask session requires from flask import session.",
      "fail_rate": 0.6,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Set secret_key at app initialization",
      "success_rate": 0.95,
      "how": "app = Flask(__name__)\napp.secret_key = 'your-secret-key'\n# Then use session\nsession['user'] = 'Alice'",
      "condition": "",
      "sources": []
    },
    {
      "action": "Check session key existence before access",
      "success_rate": 0.9,
      "how": "if 'user' in session:\n    user = session['user']\nelse:\n    user = 'Guest'",
      "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": 0.86,
  "fix_success_rate": 0.8,
  "resolvable": "true",
  "first_seen": "2024-01-25",
  "last_confirmed": "2025-01-01",
  "last_updated": "2025-01-01",
  "evidence_count": 0,
  "tags": [],
  "locale": "en",
  "aliases": []
}