Python-如何将实例变量值传递给描述符参数? [英] Python - How to pass instance variable value to descriptor parameter?

问题描述

考虑以下情况，

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，我想将self.item_num值传递给ItemList类中的定位器字典内的item_num.

In this case, I want to pass self.item_num value to item_num inside locators dictionary in ItemList class.

原因是我希望每个item_id和item_title都引用特定的item_num.

The reason is I want each of item_id and item_title refers to particular item_num.

我被困在这部分上:

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

已经创建实例后，

self.item_num值不能传递给定位器.

self.item_num value can't be passed to locators when instance is already made.

实施方式:

# 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

是否可以从实例变量更新数据描述符?

Is it possible to update data descriptor from instance variable?

如何将实例变量值传递给数据描述符参数?

How to pass instance variable value to data descriptor parameter?

其他信息:

我尝试将item_id和item_title称为实例属性，但是没有运气.我注意到这篇文章中的数据描述符不能是实例属性:数据描述符应该是类属性

I tried to call item_id and item_title as instance attribute but no luck. I noticed that data descriptor can’t be instance attribute from this post: Data descriptor should be a class attribute

物品类别:

# 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
        )

描述符:

# 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

推荐答案

我发现此，并提出了将描述符添加到对象的解决方案.

I found this article and came up with solution to add the descriptors to an object.

下面的解决方案对我有用:

This solution below worked for me:

1. 将__getattribute__和__setattr__添加到物品类别

# 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)

将类属性移动到 ItemList 构造函数中的实例属性

Move class attribute to instance attribute in ItemList constructor

# 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
        )

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