10

我正在使用https://pypi.python.org/pypi/ruamel.yaml编写一个 YAML 文件

代码是这样的:

import ruamel.yaml
from ruamel.yaml.comments import CommentedSeq

d = {}
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

    with open('test.yml', "w") as f:
        ruamel.yaml.dump(
            d, f, Dumper=ruamel.yaml.RoundTripDumper,
            default_flow_style=False, width=50, indent=8)

我只想在顶部添加评论,例如:

# Data for Class A

在 YAML 数据之前。

4

2 回答 2

9

在您的with块中,您可以将任何您想要的内容写入文件。由于您只需要在顶部添加评论,因此f.write()在调用 ruamel 之前添加一个调用:

with open('test.yml', "w") as f:
    f.write('# Data for Class A\n')
    ruamel.yaml.dump(
        d, f, Dumper=ruamel.yaml.RoundTripDumper,
        default_flow_style=False, width=50, indent=8)
于 2015-06-23T06:04:19.323 回答
4

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commentCommentTokens

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')
于 2015-06-23T06:49:45.070 回答