Validators¶
Writing validators¶
A validator is a callable that takes a value and raises a
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 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 form validation for more information on
how validators are run in forms, and 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
ModelForm
, it will run your validators on any fields
that are included in your form. See the
ModelForm documentation for information on
how model validation interacts with forms.
Built-in validators¶
The 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=None, message=None, code=None])¶ Parameters: -
regex
¶ The regular expression pattern to search for the provided
value
, or a pre-compiled regular expression. Raises aValidationError
withmessage
andcode
if no match is found. By default, matches any string (including an empty string).
-
message
¶ The error message used by
ValidationError
if validation fails. Defaults to"Enter a valid value"
.
-
code
¶ The error code used by
ValidationError
if validation fails. Defaults to"invalid"
.
-
URLValidator
¶
-
class
URLValidator
¶ A
RegexValidator
that ensures a value looks like a URL, and raises an error code of'invalid'
if it doesn’t.
validate_email
¶
-
validate_email
¶ A
RegexValidator
instance that ensures a value looks like an email address.
validate_slug
¶
-
validate_slug
¶ A
RegexValidator
instance that ensures a value consists of only letters, numbers, underscores or hyphens.
validate_ipv4_address
¶
-
validate_ipv4_address
¶ A
RegexValidator
instance that ensures a value looks like an IPv4 address.
validate_ipv6_address
¶
-
validate_ipv6_address
¶ Uses
django.utils.ipv6
to check the validity of an IPv6 address.
validate_ipv46_address
¶
-
validate_ipv46_address
¶ Uses both
validate_ipv4_address
andvalidate_ipv6_address
to ensure a value is either a valid IPv4 or IPv6 address.
validate_comma_separated_integer_list
¶
-
validate_comma_separated_integer_list
¶ A
RegexValidator
instance that ensures a value is a comma-separated list of integers.
MaxValueValidator
¶
-
class
MaxValueValidator
(max_value)¶ Raises a
ValidationError
with a code of'max_value'
ifvalue
is greater thanmax_value
.
MinValueValidator
¶
-
class
MinValueValidator
(min_value)¶ Raises a
ValidationError
with a code of'min_value'
ifvalue
is less thanmin_value
.
MaxLengthValidator
¶
-
class
MaxLengthValidator
(max_length)¶ Raises a
ValidationError
with a code of'max_length'
if the length ofvalue
is greater thanmax_length
.
MinLengthValidator
¶
-
class
MinLengthValidator
(min_length)¶ Raises a
ValidationError
with a code of'min_length'
if the length ofvalue
is less thanmin_length
.