+
−==========
+
−Validators
+
−==========
+
−
+
−.. versionadded:: 1.2
+
−.. module:: django.core.validators
+
−    :synopsis: Validation utilities and base classes
+
−
+
−Writing validators
+
−==================
+
−
+
−A validator is a callable that takes a value and raises a
+
−:exc:`~django.core.exceptions.ValidationError` if it doesn't meet some
+
−criteria. Validators can be useful for re-using validation logic between
+
−different types of fields.
+
−
+
−For example, here's a validator that only allows even numbers::
+
−
+
−    from django.core.exceptions import ValidationError
+
−
+
−    def validate_even(value):
+
−        if value % 2 != 0:
+
−            raise ValidationError(u'%s is not an even number' % value)
+
−
+
−You can add this to a model field via the field's :attr:`~django.db.models.Field.validators`
+
−argument::
+
−
+
−    from django.db import models
+
−
+
−    class MyModel(models.Model):
+
−        even_field = models.IntegerField(validators=[validate_even])
+
−
+
−Because values are converted to Python before validators are run, you can even
+
−use the same validator with forms::
+
−
+
−    from django import forms
+
−
+
−    class MyForm(forms.Form):
+
−        even_field = forms.IntegerField(validators=[validate_even])
+
−
+
−How validators are run
+
−======================
+
−
+
−See the :doc:`form validation </ref/forms/validation>` for more information on
+
−how validators are run in forms, and :ref:`Validating objects
+
−<validating-objects>` for how they're run in models. Note that validators will
+
−not be run automatically when you save a model, but if you are using a
+
−:class:`~django.forms.ModelForm`, it will run your validators on any fields
+
−that are included in your form. See the
+
−:doc:`ModelForm documentation </topics/forms/modelforms>` for information on
+
−how model validation interacts with forms.
+
−
+
−Built-in validators
+
−===================
+
−
+
−The :mod:`django.core.validators` module contains a collection of callable
+
−validators for use with model and form fields. They're used internally but
+
−are available for use with your own fields, too. They can be used in addition
+
−to, or in lieu of custom ``field.clean()`` methods.
+
−
+
−``RegexValidator``
+
−------------------
+
−.. class:: RegexValidator(regex, [message=None, code=None])
+
−
+
−    .. attribute:: regex
+
−
+
−        The regular expression pattern to search for the provided ``value``,
+
−        or a pre-compiled regular expression. Raises a
+
−        :exc:`~django.core.exceptions.ValidationError` with :attr:`.message`
+
−        and :attr:`.code` if no match is found.
+
−
+
−    .. attribute:: message
+
−
+
−        The error message used by :exc:`~django.core.exceptions.ValidationError`
+
−        if validation fails. If no :attr:`.message` is specified, a generic
+
−        ``"Enter a valid value"`` message is used. Default value: ``None``.
+
−
+
−    .. attribute:: code
+
−
+
−        The error code used by :exc:`~django.core.exceptions.ValidationError`
+
−        if validation fails. If :attr:`.code` is not specified, ``"invalid"``
+
−        is used. Default value: ``None``.
+
−
+
−``URLValidator``
+
−----------------
+
−.. class:: URLValidator([verify_exists=False, validator_user_agent=URL_VALIDATOR_USER_AGENT])
+
−
+
−    A :class:`RegexValidator` that ensures a value looks like a URL and
+
−    optionally verifies that the URL actually exists (i.e., doesn't return a
+
−    404 status code). Raises an error code of ``'invalid'`` if it doesn't look
+
−    like a URL, and a code of ``'invalid_link'`` if it doesn't exist.
+
−
+
−    .. attribute:: verify_exists
+
−
+
−        Default value: ``False``. If set to ``True``, this validator checks
+
−        that the URL actually exists.
+
−
+
−    .. attribute:: validator_user_agent
+
−
+
−        If :attr:`.verify_exists` is ``True``, Django uses the value of
+
−        :attr:`.validator_user_agent` as the "User-agent" for the request. This
+
−        defaults to :setting:`settings.URL_VALIDATOR_USER_AGENT <URL_VALIDATOR_USER_AGENT>`.
+
−
+
−``validate_email``
+
−------------------
+
−.. data:: validate_email
+
−
+
−    A :class:`RegexValidator` instance that ensures a value looks like an
+
−    e-mail address.
+
−
+
−``validate_slug``
+
−-----------------
+
−.. data:: validate_slug
+
−
+
−    A :class:`RegexValidator` instance that ensures a value consists of only
+
−    letters, numbers, underscores or hyphens.
+
−
+
−``validate_ipv4_address``
+
−-------------------------
+
−.. data:: validate_ipv4_address
+
−
+
−    A :class:`RegexValidator` instance that ensures a value looks like an IPv4
+
−    address.
+
−
+
−``validate_comma_separated_integer_list``
+
−-----------------------------------------
+
−.. data:: validate_comma_separated_integer_list
+
−
+
−    A :class:`RegexValidator` instance that ensures a value is a
+
−    comma-separated list of integers.
+
−
+
−``MaxValueValidator``
+
−---------------------
+
−.. class:: MaxValueValidator(max_value)
+
−
+
−    Raises a :exc:`~django.core.exceptions.ValidationError` with a code of
+
−    ``'max_value'`` if ``value`` is greater than ``max_value``.
+
−
+
−``MinValueValidator``
+
−---------------------
+
−.. class:: MinValueValidator(min_value)
+
−
+
−    Raises a :exc:`~django.core.exceptions.ValidationError` with a code of
+
−    ``'min_value'`` if ``value`` is less than ``min_value``.
+
−
+
−``MaxLengthValidator``
+
−----------------------
+
−.. class:: MaxLengthValidator(max_length)
+
−
+
−    Raises a :exc:`~django.core.exceptions.ValidationError` with a code of
+
−    ``'max_length'`` if the length of ``value`` is greater than ``max_length``.
+
−
+
−``MinLengthValidator``
+
−----------------------
+
−.. class:: MinLengthValidator(min_length)
+
−
+
−    Raises a :exc:`~django.core.exceptions.ValidationError` with a code of
+
−    ``'min_length'`` if the length of ``value`` is less than ``min_length``.