How to Remove '---' on Top of a Yaml File

How to remove text !!omap from yaml file?

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.

How to delete an inherit property from yaml config?

No there isn't a way to mark a key for deletion in a YAML file. You can only overwrite existing values.

And the latter is what you do, you associate the empty scalar as value to the key image as if you would have written:

  image: null   # delete

There are two things you can do: post-process or make a base mapping in your YAML file.

If you want to post-process, you associate a special unique value to image, or a specially tagged object, and after loading recursively walk over the tree to remove key-value pairs with this special value. Whether you can already do this during parsing, using hooks or overwriting some of its methods, depends on the parser.

Using a base mapping requires less work, but is more intrusive to the YAML file:

localbase: &lb
  # *tons of config*

local: &local
  image: xxx

ci:
  <<: *lb
  build: .

If you do the former you should note that if you use a parsers that preserve the "merge-hierarchy" on round-tripping (like my ruamel.yaml parser can do) it is not enough to delete the key-value pair, in that case the original from local would come back. Other parsers that simply resolve this at load time don't have this issue.

Remove property from yaml file

If you want to omit type from your whole YAML, you can Marshal your data into an object where type is not more exists

type OBJ struct {
    Id  string `yaml:"ID"`
    Mod []*Mod `yaml:"mod,omitempty"`
}

type Mod struct {
    Name        string
    //Type      string `yaml:"type"`
    Parameters  Parameters `yaml:"parameters,omitempty"`
    Build       Parameters `yaml:"build,omitempty"`
}

type will be removed, if you Marshal your data into this object.

Another solution if you do not want to use multiple object.

Use omitempty in Type. So when value of Type is "", it will be ignored

type Mod struct {
    Name       string
    Type       string `yaml:"type,omitempty"`
    Parameters  Parameters `yaml:"parameters,omitempty"`
    Build       Parameters `yaml:"build,omitempty"`
}

And do this

for i, _ := range obj.Mod {
    obj.Mod[i].Type = ""
}

Remove matching lines from yaml file

Use this (I've removed the -i, and you can add it back when you're happy with the result):

sed '/^depends:/{N;N;d}' test.yml

Details:

/^depends:/ matches the first of the three lines
{…} goups the commands to be executed when the above pattern matched
; separates successive commands
N appends the following line to the current pattern space (the line you were editing when the match occurred); this happens twice, resulting in the pattern space holding the line matching the pattern, plus the two following lines
d deletes the pattern space

Best way to remove element from Ruby hash array in yaml

require 'yaml'
ip = '1.2.3.4'
port = 3333

hash = YAML.load_file('ips.yml')
puts "hash (before): #{hash.inspect}"
hash[ip].delete(port) # here you are deleting the port (3333) from the ip (1.2.3.4)
puts "hash (after): #{hash.inspect}"
File.open('ips.yml', 'w') { |f| YAML.dump(hash, f) }

# hash (before): {"69.39.239.151"=>[7777, 8677, 8777], "69.39.239.75"=>[9677, 9377], "209.15.212.147"=>[8477, 7777], "104.156.244.109"=>[9999], "1.2.3.4"=>[3333, 4444]}
# hash (after): {"69.39.239.151"=>[7777, 8677, 8777], "69.39.239.75"=>[9677, 9377], "209.15.212.147"=>[8477, 7777], "104.156.244.109"=>[9999], "1.2.3.4"=>[4444]}