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
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.
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¶regex – If not None, overrides regex. Can be a regular
expression string or a pre-compiled regular expression.
message – If not None, overrides message.
code – If not None, overrides code.
inverse_match – If not None, overrides inverse_match.
flags – If not None, overrides flags. In that case,
regex must be a regular expression string, or
TypeError is raised.
The regular expression pattern to search for within 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).
The error message used by
ValidationError if validation fails.
Defaults to "Enter a valid value".
The error code used by ValidationError
if validation fails. Defaults to "invalid".
EmailValidator¶The error message used by
ValidationError if validation fails.
Defaults to "Enter a valid email address".
The error code used by ValidationError
if validation fails. Defaults to "invalid".
Whitelist of email domains to allow. By default, a regular expression
(the domain_regex attribute) is used to validate whatever appears
after the @ sign. However, if that string appears in the whitelist, this
validation is bypassed. If not provided, the default whitelist is
['localhost']. Other domains that don’t contain a dot won’t pass
validation, so you’d need to whitelist them as necessary.
URLValidator¶A RegexValidator that ensures a value looks like a URL, and raises
an error code of 'invalid' if it doesn’t.
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:
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.
validate_email¶An EmailValidator instance without any customizations.
validate_slug¶A RegexValidator instance that ensures a value consists of only
letters, numbers, underscores or hyphens.
validate_unicode_slug¶A RegexValidator instance that ensures a value consists of only
Unicode letters, numbers, underscores, or hyphens.
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¶A RegexValidator instance that ensures a value is a
comma-separated list of integers.
int_list_validator¶Returns a RegexValidator instance that ensures a string consists
of integers separated by sep. It allows negative integers when
allow_negative is True.
MaxValueValidator¶Raises a ValidationError with a code of
'max_value' if value is greater than limit_value, which may be
a callable.
limit_value can now be a callable.
MinValueValidator¶Raises a ValidationError with a code of
'min_value' if value is less than limit_value, which may be a
callable.
limit_value can now be a callable.
MaxLengthValidator¶Raises a ValidationError with a code of
'max_length' if the length of value is greater than
limit_value, which may be a callable.
limit_value can now be a callable.
MinLengthValidator¶Raises a ValidationError with a code of
'min_length' if the length of value is less than limit_value,
which may be a callable.
limit_value can now be a callable.
DecimalValidator¶Raises ValidationError with the following
codes:
'max_digits' if the number of digits is larger than max_digits.
'max_decimal_places' if the number of decimals is larger than
decimal_places.
'max_whole_digits' if the number of whole digits is larger than
the difference between max_digits and decimal_places.
FileExtensionValidator¶Raises a ValidationError with a code of
'invalid_extension' if the extension of value.name (value is
a File) isn’t found in allowed_extensions.
The extension is compared case-insensitively with allowed_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¶Uses Pillow to ensure that value.name (value is a
File) has a valid image extension.
ProhibitNullCharactersValidator¶Raises a ValidationError if str(value)
contains one or more nulls characters ('\x00').
The error message used by
ValidationError if validation fails.
Defaults to "Null characters are not allowed.".
The error code used by ValidationError
if validation fails. Defaults to "null_characters_not_allowed".
Dec 25, 2023