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])
You can also use a class with a __call__()
method for more complex or
configurable validators. RegexValidator
, for example, uses this
technique. If a class-based validator is used in the
validators
model field option, you should make
sure it is serializable by the migration framework by adding deconstruct() and __eq__()
methods.
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, inverse_match=None, flags=0])[source]¶Parameters: |
|
---|
regex
¶The regular expression pattern to search for the provided value
,
or a pre-compiled regular expression. By default, raises a
ValidationError
with message
and code
if a match is not found. That standard behavior can
be reversed by setting inverse_match
to True
, in which case
the ValidationError
is raised when a
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
([schemes=None, regex=None, message=None, code=None])[source]¶A RegexValidator
that ensures a value looks like a URL, and raises
an error code of 'invalid'
if it doesn’t. In addition to the optional
arguments of its parent RegexValidator
class, URLValidator
accepts an extra optional attribute:
schemes
¶URL/URI scheme list to validate against. If not provided, the default
list is ['http', 'https', 'ftp', 'ftps']
. As a reference, the IANA
Web site provides a full list of valid URI schemes.
The optional schemes
attribute was added.
validate_email
¶validate_email
¶An EmailValidator
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_ipv46_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)[source]¶Raises a ValidationError
with a code of
'max_value'
if value
is greater than max_value
.
MinValueValidator
¶MinValueValidator
(min_value)[source]¶Raises a ValidationError
with a code of
'min_value'
if value
is less than min_value
.
MaxLengthValidator
¶MaxLengthValidator
(max_length)[source]¶Raises a ValidationError
with a code of
'max_length'
if the length of value
is greater than max_length
.
MinLengthValidator
¶MinLengthValidator
(min_length)[source]¶Raises a ValidationError
with a code of
'min_length'
if the length of value
is less than min_length
.
Feb 24, 2017