您可以使用人工编写的YAML执行的操作是:
foo: &foo_anchor
key1: v1
key2: v2
key3: v3
bar:
<<: *foo_anchor
key2: override_value
我想像使用PyYAML一样以编程方式生成输出。似乎很棘手!据我所知,默认情况下,PyYAML仅在遇到相等的对象时才生成锚/引用(并且顺序可能未定义,而在此示例中,bar
必须引用foo
,而不必相反) )。我已经尝试了一些方法-定义YamlReference
类并在重写的Dumper.serialize_node
方法中检查其标记-但尝试执行以下操作:
if node.tag.endswith('magic.prefix.YamlReference'):
alias = node.value[0].value
self.emit(yaml.events.AliasEvent(alias))
super(Dumper, self).anchor_node(node.value[1])
super(Dumper, self).serialize_node(node.value[1], parent, idx)
满足预期的事件流。这可能吗?
import yaml
class Merger(object):
pass
def merger_representer(dumper, data):
return dumper.represent_scalar(u'tag:yaml.org,2002:merge', '<<')
yaml.add_representer(Merger, merger_representer)
foo = {'key1': 'v1', 'key2': 'v2', 'key3': 'v3'}
root = {
'foo': foo,
'bar': {
Merger(): foo,
'key2': 'override_value'
}
}
print(yaml.dump(root, sort_keys=False))
输出为:
foo: &id001 key1: v1 key2: v2 key3: v3 bar: <<: *id001 key2: override_value
sort_keys=False
确保键的正确顺序,它需要Python> = 3.7和PyYAML> = 5.1(感谢@tinita)。您无法控制所生成的锚名称,但是此YAML等效于您的名称。[您需要
Merger
类来强制PyYAML发出<<
(使用普通的字符串键,它将发出'<<'
,以免与合并键混淆)。
data['bar']['key1']
。当然,您需要使用适当的表示符正确转储此类。这是ruamel.yaml(免责声明,我是该软件包的作者)确实允许来回合并地图:
import sys
import ruamel.yaml
yaml_str = """\
foo: &foo_anchor
key1: v1
key2: v2
key3: v3
bar:
<<: *foo_anchor
key2: override_value
"""
yaml = ruamel.yaml.YAML()
data = yaml.load(yaml_str)
yaml.dump(data, sys.stdout)
给出:
foo: &foo_anchor key1: v1 key2: v2 key3: v3 bar: <<: *foo_anchor key2: override_value
所以我建议您看一下CommentedMap
类,这是怎么回事在constructor.py
和representer.py
中处理。如果可以升级到
ruamel.yaml
,则可以执行以下操作:
cm = ruamel.yaml.comments.CommentedMap data = cm() data['foo'] = foo = cm(key1='v1', key2='v2', key3='v3') foo.yaml_set_anchor('foo_anchor') data['bar'] = bar = cm(key2='override_value') bar.add_yaml_merge([(0, foo)]) yaml = ruamel.yaml.YAML() yaml.dump(data, sys.stdout)
从头开始,它提供了与您期望的类似的东西:
foo: &foo_anchor key1: v1 key2: v2 key3: v3 bar: <<: *foo_anchor key2: override_value
当然,以下工作按预期进行:
print(list(data['bar'].keys())) print(data['bar']['key3'])
给出:
['key2', 'key1', 'key3'] v3