# Schema validation

The simplest way to validate an instance under OAS schema is to use the `validate` function.

## Validate

To validate an OpenAPI v3.1 schema:

    from openapi_schema_validator import validate

    # A sample schema
    schema = {
        "type": "object",
        "required": [
           "name"
        ],
        "properties": {
            "name": {
                "type": "string"
            },
            "age": {
                "type": ["integer", "null"],
                "format": "int32",
                "minimum": 0,
            },
            "birth-date": {
                "type": "string",
                "format": "date",
            },
            "address": {
                 "type": 'array',
                 "prefixItems": [
                     { "type": "number" },
                     { "type": "string" },
                     { "enum": ["Street", "Avenue", "Boulevard"] },
                     { "enum": ["NW", "NE", "SW", "SE"] }
                 ],
                 "items": False,
             }
        },
        "additionalProperties": False,
    }

    # If no exception is raised by validate(), the instance is valid.
    validate({"name": "John", "age": 23, "address": [1600, "Pennsylvania", "Avenue"]}, schema)

    validate({"name": "John", "city": "London"}, schema)

    Traceback (most recent call last):
        ...
    ValidationError: Additional properties are not allowed ('city' was unexpected)

By default, the latest OpenAPI schema syntax is expected.

## Validators

if you want to disambiguate the expected schema version, import and use `OAS31Validator`:

    from openapi_schema_validator import OAS31Validator

    validate({"name": "John", "age": 23}, schema, cls=OAS31Validator)

In order to validate OpenAPI 3.0 schema, import and use `OAS30Validator` instead of `OAS31Validator`.

    from openapi_schema_validator import OAS30Validator

    # A sample schema
    schema = {
        "type": "object",
        "required": [
           "name"
        ],
        "properties": {
            "name": {
                "type": "string"
            },
            "age": {
                "type": "integer",
                "format": "int32",
                "minimum": 0,
                "nullable": True,
            },
            "birth-date": {
                "type": "string",
                "format": "date",
            }
        },
        "additionalProperties": False,
    }

    validate({"name": "John", "age": None}, schema, cls=OAS30Validator)

## Read/write context

OpenAPI 3.0 schema comes with `readOnly` and `writeOnly` keywords. In order to validate read/write context in OpenAPI 3.0 schema, import and use `OAS30ReadValidator` or `OAS30WriteValidator`.

    from openapi_schema_validator import OAS30WriteValidator

    # A sample schema
    schema = {
        "type": "object",
        "required": [
           "name"
        ],
        "properties": {
            "name": {
                "type": "string"
            },
            "age": {
                "type": "integer",
                "format": "int32",
                "minimum": 0,
                "readOnly": True,
            },
            "birth-date": {
                "type": "string",
                "format": "date",
            }
        },
        "additionalProperties": False,
    }

    validate({"name": "John", "age": 23}, schema, cls=OAS30WriteValidator)

    Traceback (most recent call last):
        ...
    ValidationError: Tried to write read-only property with 23