Inconsistent/Wrong Type casting when using yaml.dump/safe_dump

[stuartornum]

Hi,

Think I've found an issue when using yaml.dump and safe_dump. (Using pyyaml v6.0.1)

import yaml

data = {
    "buildings": [
        {
            "building_id": "0000007",
            "building_name": "100 central square"
        },{
            "building_id": "0000008",
            "building_name": "Headquarters"
        },{
            "building_id": "0000009",
            "building_name": "Test"
        },{
            "building_id": "0000010",
            "building_name": "London House"
        },
    ]
}

print(yaml.dump(data))

The output

Notice 0000008 and 0000009 are not strings, like the others.

buildings:
- building_id: '0000007'
  building_name: 100 central square
- building_id: 0000008
  building_name: Headquarters
- building_id: 0000009
  building_name: Test
- building_id: '0000010'
  building_name: London House

[perlpunk]

That's correct YAML 1.1. PyYAML implements 1.1 only so far.
A leading zero means it's an octal value, so 07 or 010 are octal numbers. 08 and 09 however can't be octal numbers, so the quotes are redundant.
Related issues: #486 (other issues are linked from there)

You can use the following project on top of PyYAML for YAML 1.2 support: https://pypi.org/project/yamlcore/
Since integers in YAML 1.2 can start with zeroes, all strings will be quoted:

>>> import yamlcore
>>> print(yaml.dump(data, Dumper=yamlcore.CoreDumper))
buildings:
- building_id: '0000007'
  building_name: 100 central square
- building_id: '0000008'
  building_name: Headquarters
- building_id: '0000009'
  building_name: Test
- building_id: '0000010'
  building_name: London House

Also see https://perlpunk.github.io/yaml-test-schema/schemas.html

[stuartornum]

Using yamlcore worked a treat! Thank you!