将类属性指定为类方法的参数 python 类对象答案

【问题标题】：Specify a class attribute as an argument to a class method python class object将类属性指定为类方法的参数 python 类对象
【发布时间】：2020-12-25 05:49:23
【问题描述】：

我创建了一个类对象如下：

class Dummy:
    def __init(self, **kwargs):
        self.__dict__ = kwargs

我创建一个类的实例如下：

dummy_df = pd.DataFrame([['Valid','NY',12],['Invalid','DD',6],['Valid','CA',18],['Valid','Total',30],['Invalid','Total',6]], columns = ['Type','Value','Count'])

dummy_dict = {'dummy_attribute':dummy_df}

dummy_instance = Dummy(**dummy_dict)

dummy_instance.dummy_attribute

      Type  Value  Count
0    Valid     NY     12
1  Invalid     DD      6
2    Valid     CA     18
3    Valid  Total     30
4  Invalid  Total      6

现在我想为 Dummy 类创建一个方法，将一个属性名称作为参数传递给该方法，并从中获取一个数据框，该数据框仅包含与该属性关联的数据框的总数。

例如，输入看起来像这样：

dummy_instance.get_totals('dummy_attribute')

输出如下：

      Type  Value  Count
3    Valid  Total     30
4  Invalid  Total      6

【问题讨论】：

标签： python class methods attributes parameter-passing

【解决方案1】：

您可以使用hasattr, getattr, setattr，查询、获取和设置类属性：

import pandas as pd

class Dummy:
    def __init__(self, **kwargs):
        for k, v in kwargs.items():
            # Checks each key as class attribute
            if not hasattr(self, k):
                # Sets key
                setattr(self, k, v)
            else:
                # Key already used!
                print("Error attribute name: %s already used!" % k)

    def get_totals(self, name):
        if not hasattr(self, name):
            print("Error: attribute not found!")
            return

        # gets the attribute from the class, like self.<name>
        df = getattr(self, name, None)
        # Filter dataframe
        return df.loc[df['Value']=='Total']



columns = ['Type','Value','Count']
dummy_df1 = pd.DataFrame([['Valid','NY',12],['Invalid','DD',6],['Valid','Total',12],['Invalid','Total',6]], columns=columns)
dummy_df2 = pd.DataFrame([['Valid','NY',22],['Invalid','DD',7],['Valid','Total',22],['Invalid','Total',7]], columns=columns)

dummy_dict = {'dummy_attribute_1': dummy_df1, 'dummy_attribute_2': dummy_df2}

dummy_instance = Dummy(**dummy_dict)
result = dummy_instance.get_totals('dummy_attribute_1')
print(result)

输出：

      Type  Value  Count
2    Valid  Total     12
3  Invalid  Total      6

【讨论】：