How to remove text "!!omap" from yaml file?

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I am trying to remove few attributes from YAML file and I am successful in doing so but it has some extra characters in the output file and not sure how to remove those.

Here is the input YAML file:

Person:
  Name: John
  Children:
    - Stacy
    - Rick
    - Josh
  Wife:
   Name: Mary 
  Id: 123

and I am expecting the YAML file as follows, after removing few attributes:

Person: 
  Name: John
  Children:
    - Rick
    - Stacy

Here is the script I am using:

import re
import time
from collections import OrderedDict

from ruamel.yaml import ruamel

file_path = '/path/to/yml/file'
# Read yaml file
config, ind, bsi = ruamel.yaml.util.load_yaml_guess_indent(open(file_path))

allowed_attributes = ['Name', 'Children']
allowed_children = ['Rick', 'Stacy']

root_node_name = 'Person'

config[root_node_name] =  OrderedDict((attribute_name, config[root_node_name][attribute_name]) for attribute_name in allowed_attributes)
config[root_node_name]['Children'] = [child_name for child_name in allowed_children]


new_file_path = f"{re.sub('.yml','',file_path)}_{time.strftime('%Y%m%d-%H%M%S')}.yml"

with open(new_file_path, "w") as fp:
    ruamel.yaml.YAML().dump(config, fp)

and this is the file it generates:

Person: !!omap
- Name: John
- Children:
  - Rick
  - Stacy
  1. How can I remove !!omap text that is on first line?
  2. How can I remove -(dash) that is next to Name and Children?

I know that having these characters in the file does not affect the functionality but I am curious as how to remove those characters that are not present in the input file.

I am using Python3 and ruamel.yaml version is 0.17.4

ruamel.yaml python-3.x yaml python
1 Answers

In YAML mappings are defined to be not ordered, although of course the keys have a definite order in the YAML document. Therefore, if you dump an explicitly ordered mapping, like Python's OrderedDict the guaranteed ordering is by dumping a sequence (always ordered) of single mappings, tagged with !!omap. If you would read that output back, you will again get an OrderedDict when using ruamel.yaml, so as you already noted there is nothing wrong (but some tools processing the output down the chain might not handle this properly).

Dictionaries in newer Python 3 implementations are ordered, and will be dumped without such tag and without the sequence needed to guarantee the order. The same effect for Python 2.7+ can be achieved by using a CommentedMap, which acts as an OrderedDict (without dumping a tag):

import sys

import ruamel.yaml 
from ruamel.yaml.comments import CommentedMap as OrderedDict

file_path = 'input.yaml'
config, ind, bsi = ruamel.yaml.util.load_yaml_guess_indent(open(file_path))
yaml = ruamel.yaml.YAML()
yaml.indent(sequence=ind, offset=bsi)  # set the original sequence indent and offset of the dash

allowed_attributes = ['Name', 'Children']
allowed_children = ['Rick', 'Stacy']

root_node_name = 'Person'

config[root_node_name] =  OrderedDict((attribute_name, config[root_node_name][attribute_name]) for attribute_name in allowed_attributes)
config[root_node_name]['Children'] = [child_name for child_name in allowed_children]


yaml.dump(config, sys.stdout)

which gives:

Person:
  Name: John
  Children:
    - Rick
    - Stacy

Please note that the officially recommended extension for files containing YAML documents is .yaml since 2007. To add to the confusion, there is an even older, but not so often encountered YML format, which is an XML derivative. So please consider updating your extensions and code.

user_13079050
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