Python - 如何將實例變量值傳遞給描述符參數？

Question

考慮下面的情況下，

ITEMLIST類：

# filename: item_list.py 

# locators dictionary is intentionally placed outside `ItemList` class 
locators = { 
    'item_id': 'css=tr:nth-of-type({item_num}) .id', 
    'item_title': 'css=tr:nth-of-type({item_num}) .alert-rules', 
    # other properties 
} 

class ItemList(Item): 
    # --- these are data descriptors --- 
    # getting item_id value based on its item_num 
    item_id = TextReadOnly(locators['item_id'].format(item_num=self.item_num)) 

    # getting item_title value based on its item_num 
    item_title = TextReadOnly(locators['item_title'].format(item_num=self.item_num)) 


    def __init__(self, context, item_num=0): 
     # self.item_num can't be passed to locators 
     self.item_num = item_num 

     super(ItemList, self).__init__(
      context 
     ) 

在這種情況下，我想通過self.item_num值item_num內定位符詞典中ItemList類。

原因是我想要item_id和item_title中的每一個都指特定的item_num。

我卡在這一部分：

item_id = TextReadOnly(locators['item_id'].format(item_num=self.item_num)) 
item_title = TextReadOnly(locators['item_title'].format(item_num=self.item_num)) 

self.item_num值不能被傳遞到定位器時，實例已經作出。

實現：

# filename: test.py 

# print item_id values from item_num=1 
item_1 = ItemList(context, 1) 
print (‘Item_id_1: ’ + item_1.id) 

# print item_id values from item_num=2 
item_2 = ItemList(context, 2) 
print (‘Item_id_2: ’ + item_2.id) 

#^no result produced from item_1.id and item_2.id because self.item_num value can't be passed to locators 

是否有可能從更新實例變量數據的描述符？

如何將實例變量值傳遞給數據描述符參數？

---

附加信息：

席力圖召item_id和item_title作爲實例屬性，但沒有運氣。我注意到，數據描述符不能從這個帖子實例屬性：Data descriptor should be a class attribute

項目類：

# filename: item.py 

import abc 


class Item(Page): 
    __metaclass__ = abc.ABCMeta 

    def __init__(self, context): 
     self.__context = context 
     super(Item, self).__init__(
      self.__context.browser 
     ) 

描述：

# filename: text_read_only.py 

class TextReadOnly(object): 
    def __init__(self, locator): 
     self.__locator = locator 

    def __get__(self, instance, owner=None): 
     try: 
      e = instance.find_element_by_locator(self.__locator) 
     except AttributeError: 
      e = instance.browser.find_element_by_locator(self.__locator) 

     return e.text 

    def __set__(self, instance, value): 
     pass 

Answer 1

我發現this article並想出瞭解決方案添加描述符到一個對象。

低於該解決方案爲我工作：

1. 添加__getattribute__和__setattr__到項目類

   # filename: item.py 
   
   import abc 
   
   
   class Item(Page): 
       __metaclass__ = abc.ABCMeta 
   
       def __init__(self, context): 
        self.__context = context 
        super(Item, self).__init__(
         self.__context.browser 
        ) 
   
       def __getattribute__(self, name): 
        value = object.__getattribute__(self, name) 
        if hasattr(value, '__get__'): 
         value = value.__get__(self, self.__class__) 
        return value 
   
       def __setattr__(self, name, value): 
        try: 
         obj = object.__getattribute__(self, name) 
        except AttributeError: 
         pass 
        else: 
         if hasattr(obj, '__set__'): 
          return obj.__set__(self, value) 
        return object.__setattr__(self, name, value) 
   

2. 移動類屬性爲實例屬性中ITEMLIST構造

   # filename: item_list.py 
   
   # locators dictionary is intentionally placed outside `ItemList` class 
   locators = { 
       'item_id': 'css=tr:nth-of-type({item_num}) .id', 
       'item_title': 'css=tr:nth-of-type({item_num}) .alert-rules', 
       # other properties 
   } 
   
   
   class ItemList(Item): 
       def __init__(self, context, item_num=0): 
        self.item_num = item_num 
        # self.item_num is able to be passed to locators 
        self.item_id = TextReadOnly(locators['item_id'].format(item_num=self.item_num)) 
        self.item_title = TextReadOnly(locators['item_title'].format(item_num=self.item_num)) 
   
        super(ItemList, self).__init__(
         context 
        )