原则上这是可能的,因为您可以往返此类“文件开头”注释,但当前的 ruamel.yaml 0.10 并没有很好地支持它,而且在“从头开始”时肯定不支持(即不更改现有的文件)。底部是一个简单的相对不错的解决方案,但我首先想介绍一个丑陋的解决方法以及如何逐步完成此操作。
丑陋的:
丑陋的做法是在将 YAML 数据写入文件之前将注释添加到文件中。那就是插入:
f.write('# Data for Class A\n')
就在之前ruamel.yaml.dump(...)
一步一步:
要在数据结构上插入注释,所以上面的hack是没有必要的,你首先需要确保你的d
数据是一个CommentedMap
类型。如果您将该d
变量与具有注释的变量的差异进行比较,则将注释的 YAML 加载回c
import ruamel.yaml
from ruamel.yaml.comments import Comment, CommentedSeq, CommentedMap
d = CommentedMap() # <<<<< most important
for m in ['B1', 'B2', 'B3']:
d2 = {}
for f in ['A1', 'A2', 'A3']:
d2[f] = CommentedSeq(['test', 'test2'])
if f != 'A2':
d2[f].fa.set_flow_style()
d[m] = d2
yaml_str = ruamel.yaml.dump(d, Dumper=ruamel.yaml.RoundTripDumper,
default_flow_style=False, width=50, indent=8)
assert not hasattr(d, Comment.attrib) # no attribute on the CommentedMap
comment = 'Data for Class A'
commented_yaml_str = '# ' + comment + '\n' + yaml_str
c = ruamel.yaml.load(commented_yaml_str, Loader=ruamel.yaml.RoundTripLoader)
assert hasattr(c, Comment.attrib) # c has the attribute
print c.ca # and this is what it looks like
print d.ca # accessing comment attribute creates it empty
assert hasattr(d, Comment.attrib) # now the CommentedMap has the attribute
这打印:
Comment(comment=[None, [CommentToken(value=u'# Data for Class A\n')]],
items={})
Comment(comment=None,
items={})
A有一个需要设置为 2 元素列表Comment
的属性,该列表由 EOL 注释(始终只有一个)和前行注释列表(以 的形式)组成comment
CommentTokens
要创建一个 CommentToken,你需要一个(假的)StartMark 来告诉它从哪一列开始:
from ruamel.yaml.error import StreamMark
start_mark = StreamMark(None, None, None, 0, None, None) # column 0
现在您可以创建令牌:
from ruamel.yaml.tokens import CommentToken
ct = CommentToken('# ' + comment + '\n', start_mark, None)
将标记分配为 CommentedMap 上前面列表的第一个元素:
d.ca.comment = [None, [ct]]
print d.ca # in case you want to check
给你:
Comment(comment=[None, [CommentToken(value='# Data for Class A\n')]],
items={})
最后:
print ruamel.yaml.dump(d, Dumper=ruamel.yaml.RoundTripDumper)
给出:
# Data for Class A
B1:
A1: [test, test2]
A3: [test, test2]
A2:
- test
- test2
B2:
A1: [test, test2]
A3: [test, test2]
A2:
- test
- test2
B3:
A1: [test, test2]
A3: [test, test2]
A2:
- test
- test2
当然你不需要创建c
对象,这只是为了说明。
你应该使用什么:为了使整个练习更容易一些,你可以忘记细节并在以下方法中修补CommentedBase
一次:
from ruamel.yaml.comments import CommentedBase
def set_start_comment(self, comment, indent=0):
"""overwrites any preceding comment lines on an object
expects comment to be without `#` and possible have mutlple lines
"""
from ruamel.yaml.error import StreamMark
from ruamel.yaml.tokens import CommentToken
if self.ca.comment is None:
pre_comments = []
self.ca.comment = [None, pre_comments]
else:
pre_comments = self.ca.comments[1]
if comment[-1] == '\n':
comment = comment[:-1] # strip final newline if there
start_mark = StreamMark(None, None, None, indent, None, None)
for com in comment.split('\n'):
pre_comments.append(CommentToken('# ' + com + '\n', start_mark, None))
if not hasattr(CommentedBase, 'set_start_comment'): # in case it is there
CommentedBase.set_start_comment = set_start_comment
然后做:
d.set_start_comment('Data for Class A')