Searching and writing in YAML file with python

Question

I have a YAML file and it has multi-document in one file.

type: ABC
api_version: v3
metadata:
  created_by: xxx
  name: cccc
namespace: zzz
spec:
  check_hooks: none
  command: bbbbb
---
type: ABC
api_version: v3
metadata:
  labels:
    aaaa.io: xxx
  created_by: me
  name: xxx
namespace: aaaa
spec:
  check_hooks: null
  command: qqqq

1. I want to read the file
2. Then I want to add one more key-value pair under the "labels" object
3. If labels object is not under metadata I want to add "labels" and then add underneath key-value pair

I have this code to load the multi-document file

with open(filepath) as stream:
    for data in yaml.safe_load_all(stream):          
        print(data)

I am able to read file and print the dict object in the console. I am not sure what to do next. I am using ruamel.yaml library.

Answer 1

You are using ruamel.yaml's old, deprecated API and you really should not for a new program. Assuming your YAML is in the file input.yaml do:

import sys
from pathlib import Path
import ruamel.yaml

in_file = Path('input.yaml')
    
yaml = ruamel.yaml.YAML()

insert_labels_at_front = True
labels = 'labels'

key = 'mykey'
val = 'myvalue'

all_docs = []
for data in yaml.load_all(in_file):
    if 'metadata' in data:
        md = data['metadata']
        if labels not in md:
            if insert_labels_at_front:
                md.insert(0, labels, {key, val})
            else:
                md[labels] = {key: val}
    all_docs.append(data)

yaml.dump_all(all_docs, sys.stdout)  # replace sys.stdout with some output Path() instance

which gives:

type: ABC
api_version: v3
metadata:
  labels: !!set
    mykey:
    myvalue:
  created_by: xxx
  name: cccc
namespace: zzz
spec:
  check_hooks: none
  command: bbbbb
---
type: ABC
api_version: v3
metadata:
  labels:
    aaaa.io: xxx
  created_by: me
  name: xxx
namespace: aaaa
spec:
  check_hooks:
  command: qqqq