在Python中的for循环中，从两个日期相同的数据框的列中减去值时出现问题

import pandas as pd

# 创建两个示例数据框
df1 = pd.DataFrame({'date': ['2022-01-01', '2022-01-02', '2022-01-03'], 'value': [10, 20, 30]})
df2 = pd.DataFrame({'date': ['2022-01-01', '2022-01-02', '2022-01-03'], 'value': [5, 10, 15]})

# 将日期列转换为datetime类型
df1['date'] = pd.to_datetime(df1['date'])
df2['date'] = pd.to_datetime(df2['date'])

# 设置索引为日期列
df1.set_index('date', inplace=True)
df2.set_index('date', inplace=True)

# 遍历数据框进行减法操作
for date, value1 in df1['value'].items():
    if date in df2.index:
        value2 = df2.loc[date, 'value']
        result = value1 - value2
        print(f"Date: {date}, Result: {result}")
    else:
        print(f"Date: {date}, Value in df2 is missing")