您的示例无效的原因仅在于您选择了保留字符来开始标量。如果*
用其他一些非保留字符替换(我倾向于使用非ASCII字符,因为它们很少被用作某些规范的一部分),那么您将得到完全合法的YAML:
paths:
root: /path/to/root/
patha: ♦root♦ + a
pathb: ♦root♦ + b
pathc: ♦root♦ + c
这将以解析器使用的语言载入映射的标准表示形式,并且不会神奇地扩展任何内容。
为此,请使用以下Python程序中的本地默认对象类型:
# coding: utf-8
from __future__ import print_function
import ruamel.yaml as yaml
class Paths:
def __init__(self):
self.d = {}
def __repr__(self):
return repr(self.d).replace('ordereddict', 'Paths')
@staticmethod
def __yaml_in__(loader, data):
result = Paths()
loader.construct_mapping(data, result.d)
return result
@staticmethod
def __yaml_out__(dumper, self):
return dumper.represent_mapping('!Paths', self.d)
def __getitem__(self, key):
res = self.d[key]
return self.expand(res)
def expand(self, res):
try:
before, rest = res.split(u'♦', 1)
kw, rest = rest.split(u'♦ +', 1)
rest = rest.lstrip() # strip any spaces after "+"
# the lookup will throw the correct keyerror if kw is not found
# recursive call expand() on the tail if there are multiple
# parts to replace
return before + self.d[kw] + self.expand(rest)
except ValueError:
return res
yaml_str = """\
paths: !Paths
root: /path/to/root/
patha: ♦root♦ + a
pathb: ♦root♦ + b
pathc: ♦root♦ + c
"""
loader = yaml.RoundTripLoader
loader.add_constructor('!Paths', Paths.__yaml_in__)
paths = yaml.load(yaml_str, Loader=yaml.RoundTripLoader)['paths']
for k in ['root', 'pathc']:
print(u'{} -> {}'.format(k, paths[k]))
它将打印:
root -> /path/to/root/
pathc -> /path/to/root/c
扩展是即时完成的,并处理嵌套的定义,但是您必须小心不要调用无限递归。
通过指定转储程序,由于动态扩展,您可以从加载的数据中转储原始YAML:
dumper = yaml.RoundTripDumper
dumper.add_representer(Paths, Paths.__yaml_out__)
print(yaml.dump(paths, Dumper=dumper, allow_unicode=True))
这将更改映射键的顺序。如果这是一个问题,则必须制作self.d
一个CommentedMap
(从导入ruamel.yaml.comments.py
)