如何用Python yaml.dump（PyYAML）在列表块前后添加空行

针对长YAML文档列表可读性差的问题，可通过自定义PyYAML的Dumper类，在列表项之间插入空行，实现预期格式。

实现代码 #

import yaml
from yaml.events import SequenceItemEvent, SequenceStartEvent

class CustomDumper(yaml.Dumper):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._is_first_sequence_item = True

    def emit(self, event):
        if isinstance(event, SequenceStartEvent):
            self._is_first_sequence_item = True
        elif isinstance(event, SequenceItemEvent) and not self._is_first_sequence_item:
            self.write_line_break()
        elif isinstance(event, SequenceItemEvent):
            self._is_first_sequence_item = False
        
        super().emit(event)

# 示例数据
network_config = {
    'interfaces': [
        {
            'name': 'phy-1_1_1',
            'description': 'Ansible: cfg phy-1_1_1',
            'breakout': 'to-four'
        },
        {
            'name': 'phy-1_1_2',
            'description': 'Interface phy-1_1_2',
            'admin_status': 'down'
        },
        {
            'name': 'phy-1_1_3',
            'description': 'Interface phy-1_1_3',
            'admin_status': 'down'
        }
    ]
}

# 生成带空行的YAML输出
print(yaml.dump(
    network_config,
    Dumper=CustomDumper,
    default_flow_style=False,
    indent=2,
    sort_keys=False
))

代码说明 #

• 自定义CustomDumper继承PyYAML原生Dumper，通过状态标记跟踪序列元素位置
• 遇到序列开始事件时，重置"是否为第一个元素"的标记
• 处理非第一个序列项时，额外写入一行空行，实现列表项之间的分隔
• 保留原生Dumper的其他功能，确保YAML格式正确性

输出效果 #

interfaces:
  - name: phy-1_1_1
    description: Ansible: cfg phy-1_1_1
    breakout: to-four

  - name: phy-1_1_2
    description: Interface phy-1_1_2
    admin_status: down

  - name: phy-1_1_3
    description: Interface phy-1_1_3
    admin_status: down

内容的提问来源于stack exchange，提问作者maloy