使用来自另一个数据帧的值过滤python中的数据帧，并为过滤值分配标签。

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2, 3, 4, 5],
                    'B': ['a', 'b', 'c', 'd', 'e']})

df2 = pd.DataFrame({'C': [2, 4],
                    'D': ['x', 'y']})

filtered_df = df1[df1['A'].isin(df2['C'])]

filtered_df['Label'] = 'Filtered'

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2, 3, 4, 5],
                    'B': ['a', 'b', 'c', 'd', 'e']})

df2 = pd.DataFrame({'C': [2, 4],
                    'D': ['x', 'y']})

filtered_df = df1[df1['A'].isin(df2['C'])]
filtered_df['Label'] = 'Filtered'

print(filtered_df)