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])
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.
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
¶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 a
ValidationError
with message
and code
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
¶URLValidator
([verify_exists=False, validator_user_agent=URL_VALIDATOR_USER_AGENT])¶A 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.
Parameters: |
|
---|
verify_exists
¶If set to True
, this validator checks that the URL actually exists.
validator_user_agent
¶If verify_exists
is True
, Django uses this value as the
“User-agent” for the request.
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
and validate_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
¶MaxValueValidator
(max_value)¶Raises a ValidationError
with a code of
'max_value'
if value
is greater than max_value
.
MinValueValidator
¶MinValueValidator
(min_value)¶Raises a ValidationError
with a code of
'min_value'
if value
is less than min_value
.
MaxLengthValidator
¶MaxLengthValidator
(max_length)¶Raises a ValidationError
with a code of
'max_length'
if the length of value
is greater than max_length
.
MinLengthValidator
¶MinLengthValidator
(min_length)¶Raises a ValidationError
with a code of
'min_length'
if the length of value
is less than min_length
.
Sep 27, 2017