如何将多年数据与每日数据在csv中求和

import csv

# 读取CSV文件
with open('data.csv', 'r') as file:
    reader = csv.reader(file)
    data = list(reader)

# 定义用于存储求和结果的字典
sum_data = {}

# 遍历多年数据和每日数据
for row in data:
    date = row[0]  # 假设日期位于第一列
    value = float(row[1])  # 假设数值位于第二列

    # 检查日期是否已存在于字典中
    if date in sum_data:
        sum_data[date] += value
    else:
        sum_data[date] = value

# 将求和结果写入新的CSV文件
with open('sum_data.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    for date, value in sum_data.items():
        writer.writerow([date, value])