1. 导入两个数据框，并查看它们的列名和数据：

import pandas as pd

df1 = pd.read_csv('file1.csv')
df2 = pd.read_csv('file2.csv')

print('df1 columns:', df1.columns)
print('df2 columns:', df2.columns)

print('df1 head:\n', df1.head())
print('df2 head:\n', df2.head())

2. 确定在哪些列上进行比较，并选择相应的列名：

compare_cols = ['From', 'To', 'Subject']

3. 使用 merge 和 np.where 方法来比较两个数据框中的邮件数据：

import numpy as np

merged = df1.merge(df2, on=compare_cols, how='outer', suffixes=['_df1', '_df2'])
merged['comparison'] = np.where(merged.isna().sum(axis=1) == 0, 'match', 'mismatch')

4. 查看比较结果：

print('Comparison results:\n', merged[['From', 'To', 'Subject', 'comparison']])