覆蓋GAE上的__setattr__ db.Model python 2.7

Question

GAE db.Model無法存儲元組列表。因此，我需要將列表保存爲json.dumps字符串，並且在將該列表從實體中拉出時，json.loads該字符串。我想自動執行此操作。這裏是我的嘗試：

class example(db.Model): 
    someAttr = db.StringListProperty() 
    A = db.StringProperty() 
    B = db.StringProperty() 
    C = db.StringProperty() 

    def __setattr__(self, name, value): 
     #convert json to string for storage 
     if name in ("A", "B", "C"): 
      value = json.dumps(value) 
     #call default set method 
     return super(Quote, self).__setattr__(name, value) 

    def __getattribute__(self, name): 
     #convert string to json for retrieval 
     if name in ("A", "B", "C"): 
      val = super(Quote, self).__getattribute__(name) 
      return json.loads(val) 
     else: 
      # default get behavior 
      return super(Quote, self).__getattribute__(name) 

當我嘗試設置A，B，C實體的屬性，我得到：

BadValueError: Property C must be a str or unicode instance, not a list 

Answer 1

如果您不需要存儲非常大JSONs，我建議你看看NDB。它內置了JsonProperty：https://developers.google.com/appengine/docs/python/ndb/properties#types。

我也碰到過在App Engine中GOOGL集團一個有趣的貼子，討論存儲大量JSONs的更有效的方法：https://groups.google.com/forum/#!msg/google-appengine/WPfAvHDGNjQ/XfakEMm1qzoJ