Python - 如何将实例变量值传递给描述符参数？

Question

考虑下面的情况下，

ITEMLIST类：

# 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 
     ) 

在这种情况下，我想通过self.item_num值item_num内定位符词典中ItemList类。

原因是我想要item_id和item_title中的每一个都指特定的item_num。

我卡在这一部分：

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值不能被传递到定位器时，实例已经作出。

实现：

# 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 

是否有可能从更新实例变量数据的描述符？

如何将实例变量值传递给数据描述符参数？

---

附加信息：

席力图召item_id和item_title作为实例属性，但没有运气。我注意到，数据描述符不能从这个帖子实例属性：Data descriptor should be a class attribute

项目类：

# 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

我发现this article并想出了解决方案添加描述符到一个对象。

低于该解决方案为我工作：

1. 添加__getattribute__和__setattr__到项目类

   # 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. 移动类属性为实例属性中ITEMLIST构造

   # 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 
        )