如果行键不存在，则为python csv编写器

import csv

def write_to_csv(file_path, row_key, data):
    # 检查文件是否存在
    file_exists = False
    try:
        with open(file_path, 'r') as file:
            reader = csv.DictReader(file)
            for row in reader:
                if row['key'] == row_key:
                    file_exists = True
                    break
    except FileNotFoundError:
        pass

    # 写入数据
    with open(file_path, 'a', newline='') as file:
        fieldnames = ['key', 'data']
        writer = csv.DictWriter(file, fieldnames=fieldnames)

        if not file_exists:
            writer.writeheader()  # 写入表头

        writer.writerow({'key': row_key, 'data': data})

# 示例用法
file_path = 'data.csv'
row_key = '123'
data = 'example data'
write_to_csv(file_path, row_key, data)