Validating a yaml document in python

Question

One of the benefits of XML is being able to validate a document against an XSD. YAML doesn\'t have this feature, so how can I validate that the YAML document I open is in th

Answer 1

I find Cerberus to be very reliable with great documentation and straightforward to use.

Here is a basic implementation example:

my_yaml.yaml:

name: 'my_name'
date: 2017-10-01
metrics:
    percentage:
    value: 87
    trend: stable

Defining the validation schema in schema.py:

{
    'name': {
        'required': True,
        'type': 'string'
    },
    'date': {
        'required': True,
        'type': 'date'
    },
    'metrics': {
        'required': True,
        'type': 'dict',
        'schema': {
            'percentage': {
                'required': True,
                'type': 'dict',
                'schema': {
                    'value': {
                        'required': True,
                        'type': 'number',
                        'min': 0,
                        'max': 100
                    },
                    'trend': {
                        'type': 'string',
                        'nullable': True,
                        'regex': '^(?i)(down|equal|up)$'
                    }
                }
            }
        }
    }
}

Using the PyYaml to load a yaml document:

import yaml
def load_doc():
    with open('./my_yaml.yaml', 'r') as stream:
        try:
            return yaml.load(stream)
        except yaml.YAMLError as exception:
            raise exception

## Now, validating the yaml file is straightforward:
from cerberus import Validator
schema = eval(open('./schema.py', 'r').read())
    v = Validator(schema)
    doc = load_doc()
    print(v.validate(doc, schema))
    print(v.errors)

Keep in mind that Cerberus is an agnostic data validation tool, which means that it can support formats other than YAML, such as JSON, XML and so on.