CODEWITHSUNDEEP
pythonpython-3.xparsingyamlruamel.yaml
David
David

Reputation: 1569

How do I append to a YAML file with python

I have a YAML file called data.yaml: 

---
'001':
  name: Ben
  email: [email protected]

I would like to have an updated file that looks like this: 

---
'001':
  name: Ben
  email: [email protected]
'002':
  name: Lisa
  email: [email protected]
  numbers: 
    - 000-111-2222
    - 000-111-2223

How do I achieve this in python using yaml package/s?

Edit:

I have tried: 

import yaml
import io

data = {'002': {'name': 'Lisa', 'email': '[email protected]', 'numbers': ['000-111-2222', '000-111-2223']}}

with io.open('data.yaml', 'w', encoding='utf8') as outfile:
    yaml.safe_dump(data, outfile, default_flow_style=False, allow_unicode=True)

Method safe_dump overrides the file content and I only see this as the new file content!

'002':
  name: Lisa
  email: [email protected]
  numbers: 
    - 000-111-2222
    - 000-111-2223

Upvotes: 1

Views: 8141

Answers (1)

Anthon
Anthon

Reputation: 76568

You can, in general, not add to a YAML document in a file by just writing extra information at the end of that file. This migth work for YAML documents that have a mapping or sequence at the top level that is block style, but even then simply appending can only work for certain cases of documents.

It is easy to just load your YAML to Python datastructure, update/extend that structure and then dump it back. That way you don't have to deal with potential duplicate keys, non-bare documents and other issues that will result in invalid YAML when you use simple appending. Assumping your original file is called input.yaml, the following does the trick:

import sys
from pathlib import Path
import ruamel.yaml

file_name = Path('input.yaml')

record_to_add = dict(name='Lisa', email='[email protected]', numbers=['000-111-2222', '000-111-2223'])

yaml = ruamel.yaml.YAML()
yaml.explicit_start = True
data = yaml.load(file_name)
data['002'] = record_to_add
yaml.dump(data, sys.stdout)

which gives:

---
'001':
  name: Ben
  email: [email protected]
'002':
  name: Lisa
  email: [email protected]
  numbers:
  - 000-111-2222
  - 000-111-2223

Upvotes: 4

Related Questions