Fields are defined as properties of a Model class object:

from tortoise.models import Model
from tortoise import fields

class Tournament(Model):
    id = fields.IntField(pk=True)
    name = fields.CharField(max_length=255)

.. rst-class:: emphasize-children

Here is the list of fields available with custom options of these fields:

.. automodule:: tortoise.fields.base
    :members:
    :undoc-members:
    :exclude-members: field_type, indexable, has_db_field, skip_to_python_if_native, allows_generated, function_cast, SQL_TYPE, GENERATED_SQL

.. automodule:: tortoise.fields.data
    :members:
    :exclude-members: to_db_value, to_python_value

.. automodule:: tortoise.fields.relational
    :members: ForeignKeyField, OneToOneField, ManyToManyField
    :exclude-members: to_db_value, to_python_value

.. automodule:: tortoise.contrib.mysql.fields
    :members: GeometryField

.. automodule:: tortoise.contrib.postgres.fields
    :members: TSVectorField

It is possible to subclass fields allowing use of arbitrary types as long as they can be represented in a database compatible format. An example of this would be a simple wrapper around the :class:`~tortoise.fields.CharField` to store and query Enum types.

from enum import Enum
from typing import Type

from tortoise import ConfigurationError
from tortoise.fields import CharField


class EnumField(CharField):
    """
    An example extension to CharField that serializes Enums
    to and from a str representation in the DB.
    """

    def __init__(self, enum_type: Type[Enum], **kwargs):
        super().__init__(128, **kwargs)
        if not issubclass(enum_type, Enum):
            raise ConfigurationError("{} is not a subclass of Enum!".format(enum_type))
        self._enum_type = enum_type

    def to_db_value(self, value: Enum, instance) -> str:
        return value.value

    def to_python_value(self, value: str) -> Enum:
        try:
            return self._enum_type(value)
        except Exception:
            raise ValueError(
                "Database value {} does not exist on Enum {}.".format(value, self._enum_type)
            )

When subclassing, make sure that the to_db_value returns the same type as the superclass (in the case of CharField, that is a str) and that, naturally, to_python_value accepts the same type in the value parameter (also str).