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 reusing validation logic between
different types of fields.
For example, here’s a validator that only allows even numbers:
from django.core.exceptions import ValidationError
from django.utils.translation import gettext_lazy as _
def validate_even(value):
if value % 2 != 0:
raise ValidationError(
_("%(value)s is not an even number"),
params={"value": 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.
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, inverse_match=None, flags=0)[source]¶ Parameters: - regex – If not
None
, overridesregex
. Can be a regular expression string or a pre-compiled regular expression. - message – If not
None
, overridesmessage
. - code – If not
None
, overridescode
. - inverse_match – If not
None
, overridesinverse_match
. - flags – If not
None
, overridesflags
. In that case,regex
must be a regular expression string, orTypeError
is raised.
A
RegexValidator
searches the providedvalue
for a given regular expression withre.search()
. By default, raises aValidationError
withmessage
andcode
if a match is not found. Its behavior can be inverted by settinginverse_match
toTrue
, in which case theValidationError
is raised when a match is found.-
regex
¶ The regular expression pattern to search for within the provided
value
, usingre.search()
. This may be a string or a pre-compiled regular expression created withre.compile()
. Defaults to the empty string, which will be found in every possiblevalue
.
-
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"
.
- regex – If not
EmailValidator
¶
-
class
EmailValidator
(message=None, code=None, allowlist=None)[source]¶ Parameters: An
EmailValidator
ensures that a value looks like an email, and raises aValidationError
withmessage
andcode
if it doesn’t. Values longer than 320 characters are always considered invalid.-
message
¶ The error message used by
ValidationError
if validation fails. Defaults to"Enter a valid email address"
.
-
code
¶ The error code used by
ValidationError
if validation fails. Defaults to"invalid"
.
-
allowlist
¶ Allowlist of email domains. By default, a regular expression (the
domain_regex
attribute) is used to validate whatever appears after the@
sign. However, if that string appears in theallowlist
, this validation is bypassed. If not provided, the defaultallowlist
is['localhost']
. Other domains that don’t contain a dot won’t pass validation, so you’d need to add them to theallowlist
as necessary.
Changed in Django 3.2.20:In older versions, values longer than 320 characters could be considered valid.
-
URLValidator
¶
-
class
URLValidator
(schemes=None, regex=None, message=None, code=None)[source]¶ A
RegexValidator
subclass that ensures a value looks like a URL, and raises an error code of'invalid'
if it doesn’t. Values longer thanmax_length
characters are always considered invalid.Loopback addresses and reserved IP spaces are considered valid. Literal IPv6 addresses (RFC 3986#section-3.2.2) and Unicode domains are both supported.
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 website provides a full list of valid URI schemes.
-
max_length
¶ - New in Django 3.2.20.
The maximum length of values that could be considered valid. Defaults to 2048 characters.
Changed in Django 3.2.20:In older versions, values longer than 2048 characters could be considered valid.
-
validate_email
¶
-
validate_email
¶ An
EmailValidator
instance without any customizations.
validate_slug
¶
-
validate_slug
¶ A
RegexValidator
instance that ensures a value consists of only letters, numbers, underscores or hyphens.
validate_unicode_slug
¶
-
validate_unicode_slug
¶ A
RegexValidator
instance that ensures a value consists of only Unicode letters, numbers, underscores, or hyphens.
validate_ipv4_address
¶
-
validate_ipv4_address
[source]¶ 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.
int_list_validator
¶
-
int_list_validator
(sep=',', message=None, code='invalid', allow_negative=False)[source]¶ Returns a
RegexValidator
instance that ensures a string consists of integers separated bysep
. It allows negative integers whenallow_negative
isTrue
.
MaxValueValidator
¶
-
class
MaxValueValidator
(limit_value, message=None)[source]¶ Raises a
ValidationError
with a code of'max_value'
ifvalue
is greater thanlimit_value
, which may be a callable.
MinValueValidator
¶
-
class
MinValueValidator
(limit_value, message=None)[source]¶ Raises a
ValidationError
with a code of'min_value'
ifvalue
is less thanlimit_value
, which may be a callable.
MaxLengthValidator
¶
-
class
MaxLengthValidator
(limit_value, message=None)[source]¶ Raises a
ValidationError
with a code of'max_length'
if the length ofvalue
is greater thanlimit_value
, which may be a callable.
MinLengthValidator
¶
-
class
MinLengthValidator
(limit_value, message=None)[source]¶ Raises a
ValidationError
with a code of'min_length'
if the length ofvalue
is less thanlimit_value
, which may be a callable.
DecimalValidator
¶
-
class
DecimalValidator
(max_digits, decimal_places)[source]¶ Raises
ValidationError
with the following codes:'max_digits'
if the number of digits is larger thanmax_digits
.'max_decimal_places'
if the number of decimals is larger thandecimal_places
.'max_whole_digits'
if the number of whole digits is larger than the difference betweenmax_digits
anddecimal_places
.
FileExtensionValidator
¶
-
class
FileExtensionValidator
(allowed_extensions, message, code)[source]¶ Raises a
ValidationError
with a code of'invalid_extension'
if the extension ofvalue.name
(value
is aFile
) isn’t found inallowed_extensions
. The extension is compared case-insensitively withallowed_extensions
.Warning
Don’t rely on validation of the file extension to determine a file’s type. Files can be renamed to have any extension no matter what data they contain.
validate_image_file_extension
¶
-
validate_image_file_extension
[source]¶ Uses Pillow to ensure that
value.name
(value
is aFile
) has a valid image extension.
ProhibitNullCharactersValidator
¶
-
class
ProhibitNullCharactersValidator
(message=None, code=None)[source]¶ Raises a
ValidationError
ifstr(value)
contains one or more null characters ('\x00'
).Parameters: -
message
¶ The error message used by
ValidationError
if validation fails. Defaults to"Null characters are not allowed."
.
-
code
¶ The error code used by
ValidationError
if validation fails. Defaults to"null_characters_not_allowed"
.
-
StepValueValidator
¶
-
class
StepValueValidator
(limit_value, message=None, offset=None)[source]¶ Raises a
ValidationError
with a code of'step_size'
ifvalue
is not an integral multiple oflimit_value
, which can be a float, integer or decimal value or a callable. Whenoffset
is set, the validation occurs againstlimit_value
plusoffset
. For example, forStepValueValidator(3, offset=1.4)
valid values include1.4
,4.4
,7.4
,10.4
, and so on.Changed in Django 5.0:The
offset
argument was added.