有没有办法在 Python 中往返转储 YAML 时保留订单？

Question

我正在尝试从 YAML 文件中加载一些数据并将其放回：

services:
  dc01:
    sw-06-50001:
      servers:
      - {ip: 10.255.206.12, port: 50001, weight: 100}
      - {ip: 10.255.206.13, port: 50001, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50001}
    sw-09-50002:
      servers:
      - {ip: 10.255.206.18, port: 50002, weight: 100}
      - {ip: 10.255.206.19, port: 50002, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50002}
    sw-06-50003:
      servers:
      - {ip: 10.255.206.12, port: 50003, weight: 100}
      - {ip: 10.255.206.13, port: 50003, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50003}
    sw-09-50004:
      servers:
      - {ip: 10.255.206.18, port: 50004, weight: 100}
      - {ip: 10.255.206.19, port: 50004, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50004}

用这个：

import ruamel.yaml as yaml
with open('filename.yml', 'r') as stream:
    outdata = yaml.load(stream,Loader=yaml.Loader)

yaml.dump(outdata,'filename_out.yml')

我需要保留列表中的所有格式和数据顺序，但输出转储会导致按 sw-xx.. 键按字母顺序排序：

services:
  dc01:
    sw-06-50001:
      servers:
      - {ip: 10.255.206.12, port: 50001, weight: 100}
      - {ip: 10.255.206.13, port: 50001, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50001}

    sw-06-50003:
      servers:
      - {ip: 10.255.206.12, port: 50003, weight: 100}
      - {ip: 10.255.206.13, port: 50003, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50003}
    sw-09-50002:
      servers:
      - {ip: 10.255.206.18, port: 50002, weight: 100}
      - {ip: 10.255.206.19, port: 50002, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50002}
    sw-09-50004:
      servers:
      - {ip: 10.255.206.18, port: 50004, weight: 100}
      - {ip: 10.255.206.19, port: 50004, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50004}

转储时如何保持条目的原始顺序？

Answer 1

您正在执行往返，但您没有使用 ruamel.yaml 的往返功能。相反，你是 使用过时的 PyYAML 兼容性 load 和 dump 函数。

相反，您应该实例化一个ruamel.yaml.YAML() 实例并使用该实例的load 和dump 方法， 它们默认为往返并保留顺序（以及 cmets、标签名称等）

import sys
import ruamel.yaml

yaml_str = """\
services:
  dc01:
    sw-06-50001:  # first
      servers:
      - {ip: 10.255.206.12, port: 50001, weight: 100}
      - {ip: 10.255.206.13, port: 50001, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50001}
    sw-09-50002:
      servers:
      - {ip: 10.255.206.18, port: 50002, weight: 100}
      - {ip: 10.255.206.19, port: 50002, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50002}
    sw-06-50003:  # third
      servers:
      - {ip: 10.255.206.12, port: 50003, weight: 100}
      - {ip: 10.255.206.13, port: 50003, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50003}
    sw-09-50004:
      servers:
      - {ip: 10.255.206.18, port: 50004, weight: 100}
      - {ip: 10.255.206.19, port: 50004, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50004}
"""

yaml = ruamel.yaml.YAML()
# yaml.indent(mapping=4, sequence=4, offset=2)
# yaml.preserve_quotes = True
data = yaml.load(yaml_str)
yaml.dump(data, sys.stdout)

给出：

services:
  dc01:
    sw-06-50001:  # first
      servers:
      - {ip: 10.255.206.12, port: 50001, weight: 100}
      - {ip: 10.255.206.13, port: 50001, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50001}
    sw-09-50002:
      servers:
      - {ip: 10.255.206.18, port: 50002, weight: 100}
      - {ip: 10.255.206.19, port: 50002, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50002}
    sw-06-50003:  # third
      servers:
      - {ip: 10.255.206.12, port: 50003, weight: 100}
      - {ip: 10.255.206.13, port: 50003, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50003}
    sw-09-50004:
      servers:
      - {ip: 10.255.206.18, port: 50004, weight: 100}
      - {ip: 10.255.206.19, port: 50004, weight: 90}
      virtual: {ip: 192.168.1.4, port: 50004}

或者，如果您在文件中有 YAML：

from pathlib import Path
from ruamel.yaml import YAML

# the recommended extension for YAML files has been .yaml since 2006.
file_name = Path('filename.yaml')  
file_out = Path('filename_out.yaml')

yaml = YAML()
outdata = yaml.load(file_name)
yaml.dump(outdata, file_out)