如何替换文件中以特定字符串开头的列表中的第4项？

# 1. 读取文件
with open('file.txt', 'r') as file:
    content = file.readlines()

# 2. 解析文件内容
data = []
for line in content:
    data.append(line.strip().split(','))

# 3. 查找目标列表
target_list = None
for item in data:
    if item[0].startswith('特定字符串'):
        target_list = item
        break

# 4. 替换第4项
if target_list is not None and len(target_list) >= 4:
    target_list[3] = '新的值'

# 5. 更新文件内容
updated_content = []
for item in data:
    updated_content.append(','.join(item))

# 6. 写入文件
with open('file.txt', 'w') as file:
    file.write('\n'.join(updated_content))