在csv文件中添加新列和来自不同字典的值-理解

import csv

# 打开csv文件
with open('data.csv', 'r') as file:
    # 读取csv文件
    reader = csv.reader(file)
    # 获取表头
    header = next(reader)
    
    # 创建新列
    new_column_name = '新列'
    header.append(new_column_name)
    
    # 获取字典的值
    dict1 = {'A': '值1', 'B': '值2'}
    dict2 = {'C': '值3', 'D': '值4'}
    
    # 遍历每一行数据
    for row in reader:
        # 根据某个字段的值从字典中获取对应的值
        field_value = row[0]  # 假设第一个字段为需要匹配的字段
        if field_value in dict1:
            value = dict1[field_value]
        elif field_value in dict2:
            value = dict2[field_value]
        else:
            value = '未知'
        
        # 将值写入新列
        row.append(value)
    
    # 保存csv文件
    with open('data_new.csv', 'w', newline='') as new_file:
        writer = csv.writer(new_file)
        writer.writerow(header)
        writer.writerows(reader)