无法添加列表成员

Question

I'm trying to add a new list member but I'm not being successful.

This is what I have:

import sys
from ruamel.yaml import YAML
from ruamel.yaml.comments import CommentedMap as cm
from ruamel.yaml.comments import CommentedSeq as cs

yaml_doc = """\
Condition:
  Like:
    - !Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']]
"""
yaml = YAML()
yaml.preserve_quotes = True
yaml.width = 4096
data = yaml.load(yaml_doc)
ref = data['Condition']['Like']

new_member = "!Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '456', ':tty:*']]"
# new_member2 = '!Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '456', ':tty:*']]'

ref.append(new_member)
# ref.append(new_member2)

yaml.dump(data, sys.stdout)

The output is

Condition:
  Like:
  - !Join ['', ['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']]
  - "!Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '456', ':tty:*']]"

I do not want the double quotes.

If I uncomment the section related to the new_member2 I get and error

  File "ec2-recover-2.py", line 18
    new_member2 = '!Join ['',['abc: def: ', !Ref 'XYZ: : Rert', ': ', '456', ': tty: *']]'
                                 ^
SyntaxError: invalid syntax

How can I add a member list in this format !Join ['', ['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']] and it not having single or double quotes in the final YAML?

Answer 1

You seem to be thinking that this:

!Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']]

is a plain scalar that gets loaded as a string in Python. It is not. A plain scalar cannot start with an exclamation mark, as YAML uses that to introduces a tag , and what you load from there is quite a complicated object:

import ruamel.yaml

yaml = ruamel.yaml.YAML()
data = yaml.load("!Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']]")
print(data)

prints:

['', ['abc:def:', <ruamel.yaml.comments.TaggedScalar object at 0x7f405265fa58>, ':', '123', ':tty:*']]

You can build such objects from scratch, but it is probably more easy, to load the list item you want to add, from its YAML string representation. If you want to engage in some DIY, you can construct it the entry from CommentedSeq and TaggedScalar instances as well:

import sys
from ruamel.yaml import YAML
from ruamel.yaml.comments import CommentedSeq as cs
from ruamel.yaml.comments import TaggedScalar as ts
from ruamel.yaml.scalarstring import SingleQuotedScalarString as sq

yaml_doc = """\
Condition:
  Like:
    - !Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']]
"""
yaml = YAML()
yaml.preserve_quotes = True
yaml.width = 4096
data = yaml.load(yaml_doc)
ref = data['Condition']['Like']

new_member = yaml.load("!Join ['',['abc:def:', !Ref 'XYZ::Rert', ':', '456', ':tty:*']]")

ts1 = ts()
ts1.value = 'XYZ::Rert'
ts1.style = "'"
ts1.yaml_set_tag('!Ref')

new_member2 = cs([sq(''), [sq('abc:def:'), ts1 , sq(':'), sq('789'), sq(':tty:*')]])
new_member2.yaml_set_tag('!Join')
new_member2.fa.set_flow_style()

ref.append(new_member)
ref.append(new_member2)

yaml.dump(data, sys.stdout)

which gives:

Condition:
  Like:
  - !Join ['', ['abc:def:', !Ref 'XYZ::Rert', ':', '123', ':tty:*']]
  - !Join ['', ['abc:def:', !Ref 'XYZ::Rert', ':', '456', ':tty:*']]
  - !Join ['', ['abc:def:', !Ref 'XYZ::Rert', ':', '789', ':tty:*']]

(If you really want to figure out how to construct something like new_member2 yourself, it helps to load the output you want from YAML and print the individual items, their types and their attributes)