如何在ruamel.yaml中保留换行格式实现无损往返更新？

要实现仅修改value字段，同时严格保留原YAML文件中description的多行折叠格式和url的单行长文本格式，需要调整ruamel.yaml的几个关键参数：

关键参数说明 #

• keep_folded=True：强制保留原文件中用>标记的折叠块字符串的换行结构，避免被合并为单行。
• width=9999：设置足够大的行宽阈值，防止长URL文本被自动换行。
• preserve_quotes=True：保留原文件中字符串的引号格式（如果有），确保格式完全一致。

完整代码示例 #

from ruamel.yaml import YAML

# 初始化YAML处理器，配置格式保留参数
yaml = YAML()
yaml.keep_folded = True
yaml.width = 9999
yaml.preserve_quotes = True

# 加载原YAML文件
with open('input.yaml', 'r') as f:
    yaml_data = yaml.load(f)

# 仅修改value字段
yaml_data['value'] = 'updated_value'

# 写入更新后的文件，保留原格式
with open('output.yaml', 'w') as f:
    yaml.dump(yaml_data, f)

示例对比 #

原输入文件（input.yaml） #

description: >
  This is a long description
  that spans multiple lines
  in the original file
url: https://example.com/very/long/url/that/should/not/be/wrapped/even/though/it/is/extremely/long/and/goes/on/for/quite/a/while
value: old_value

默认设置下的错误输出 #

description: This is a long description that spans multiple lines in the original file
url: https://example.com/very/long/url/that/should/not/be/wrapped/even/though/it/is/
extremely/long/and/goes/on/for/quite/a/while
value: updated_value

设置width=999后的错误输出 #

description: This is a long description that spans multiple lines in the original file
url: https://example.com/very/long/url/that/should/not/be/wrapped/even/though/it/is/extremely/long/and/goes/on/for/quite/a/while
value: updated_value

期望输出（配置正确后得到） #

description: >
  This is a long description
  that spans multiple lines
  in the original file
url: https://example.com/very/long/url/that/should/not/be/wrapped/even/though/it/is/extremely/long/and/goes/on/for/quite/a/while
value: updated_value

内容的提问来源于stack exchange，提问作者crdavis