如何使用ruamel.yaml在Python中向YAML插入注释行？

Question

我有一个这样的结构,我想使用ruamel.yaml以下命令添加注释行:

xyz:
  a: 1    # comment 1
  b: 2

test1:
  test2:
    test3: 3

现在,我想插入注释行(而不是eol_comments)使它看起来像这样:

xyz:
  a: 1    # comment 1
  b: 2

# before test1 (top level)
test1:
  # before test2
  test2:
    # after test2
    test3: 3

我知道,我可以使用添加eol_comments ruamel.yaml,但我没有找到添加整个注释行的方法.

Answer 1

确实没有函数在ruamel.yaml<=0.12.18键之前的行上插入注释,但是有一个函数可以在结构的开头设置注释:.yaml_set_start_comment.有了它,您可以设置要添加的三个注释中的两个:

import sys
import ruamel.yaml

yaml_str = """\
xyz:
  a: 1    # comment 1
  b: 2

test1:
  test2:
    test3: 3
"""

data = ruamel.yaml.round_trip_load(yaml_str)
data['test1'].yaml_set_start_comment('before test2', indent=2)
data['test1']['test2'].yaml_set_start_comment('after test2', indent=4)
ruamel.yaml.round_trip_dump(data, sys.stdout)

得到:

xyz:
  a: 1    # comment 1
  b: 2

test1:
  # before test2
  test2:
    # after test2
    test3: 3

实际上有一个"注释"构成了xyz和的值之间的空行test1,但是如果您将注释附加到该结构,然后在test1事物未显示之前插入新键.因此,要做的是在key之前显式插入注释test1.您可以往返加载预期输出以查看内部Comment应该是什么样的:

yaml_str_out = """\
xyz:
  a: 1    # comment 1
  b: 2

# before test1 (top level)
test1:
  # before test2
  test2:
    # before test3
    test3: 3
"""
test = ruamel.yaml.round_trip_load(yaml_str_out)
print(test.ca)

给(包装这个以便于查看):

Comment(comment=None,
        items={'test1': [None, 
                        [CommentToken(value='# before test1 (top level)\n')], 
                        None, 
                        [CommentToken(value='# before test2\n')]]})

如您所见,# before test2被认为是关键后的评论.和做test['test1'].yaml_set_start_comment('xxxxx', indent=2)不会有与相关的评论任何影响test1否决这一点,# xxxxx将不会在转储显示.

有了这些信息和一些背景知识,我修改了一些代码yaml_set_start_comment()(假设原始导入和yaml_str):

def yscbak(self, key, before=None, indent=0, after=None, after_indent=None):
    """
    expects comment (before/after) to be without `#` and possible have multiple lines
    """
    from ruamel.yaml.error import Mark
    from ruamel.yaml.tokens import CommentToken

    def comment_token(s, mark):
        # handle empty lines as having no comment
        return CommentToken(('# ' if s else '') + s + '\n', mark, None)

    if after_indent is None:
        after_indent = indent + 2
    if before and before[-1] == '\n':
        before = before[:-1]  # strip final newline if there
    if after and after[-1] == '\n':
        after = after[:-1]  # strip final newline if there
    start_mark = Mark(None, None, None, indent, None, None)
    c = self.ca.items.setdefault(key, [None, [], None, None])
    if before:
        for com in before.split('\n'):
            c[1].append(comment_token(com, start_mark))
    if after:
        start_mark = Mark(None, None, None, after_indent, None, None)
        if c[3] is None:
            c[3] = []
        for com in after.split('\n'):
            c[3].append(comment_token(com, start_mark))

if not hasattr(ruamel.yaml.comments.CommentedMap, 
               'yaml_set_comment_before_after_key'):
    ruamel.yaml.comments.CommentedMap.yaml_set_comment_before_after_key = yscbak


data = ruamel.yaml.round_trip_load(yaml_str)
data.yaml_set_comment_before_after_key('test1', 'before test1 (top level)',
                                       after='before test2', after_indent=2)
data['test1']['test2'].yaml_set_start_comment('after test2', indent=4)
ruamel.yaml.round_trip_dump(data, sys.stdout)

得到:

xyz:
  a: 1    # comment 1
  b: 2

# before test1 (top level)
test1:
  # before test2
  test2:
    # after test2
    test3: 3

测试hasattr是为了确保在添加时不会覆盖这样的函数ruamel.yaml

顺便说一句:所有评论都是YAML中的行尾评论,在其中一些评论之前可能只有有效的YAML.