A validator is a callable that takes a value and raises a\nValidationError if it doesn’t meet some\ncriteria. Validators can be useful for re-using validation logic between\ndifferent types of fields.
For example, here’s a validator that only allows even numbers:
\nfrom django.core.exceptions import ValidationError\nfrom django.utils.translation import gettext_lazy as _\n\ndef validate_even(value):\n if value % 2 != 0:\n raise ValidationError(\n _('%(value)s is not an even number'),\n params={'value': value},\n )\nYou can add this to a model field via the field’s validators\nargument:
from django.db import models\n\nclass MyModel(models.Model):\n even_field = models.IntegerField(validators=[validate_even])\nBecause values are converted to Python before validators are run, you can even\nuse the same validator with forms:
\nfrom django import forms\n\nclass MyForm(forms.Form):\n even_field = forms.IntegerField(validators=[validate_even])\nYou can also use a class with a __call__() method for more complex or\nconfigurable validators. RegexValidator, for example, uses this\ntechnique. If a class-based validator is used in the\nvalidators model field option, you should make\nsure it is serializable by the migration framework by adding deconstruct() and __eq__() methods.
See the form validation for more information on\nhow validators are run in forms, and Validating objects for how they’re run in models. Note that validators will\nnot be run automatically when you save a model, but if you are using a\nModelForm, it will run your validators on any fields\nthat are included in your form. See the\nModelForm documentation for information on\nhow model validation interacts with forms.
The django.core.validators module contains a collection of callable\nvalidators for use with model and form fields. They’re used internally but\nare available for use with your own fields, too. They can be used in addition\nto, or in lieu of custom field.clean() methods.
RegexValidatorLink to this heading#regex – If not None, overrides regex. Can be a regular\nexpression 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,\nregex must be a regular expression string, or\nTypeError is raised.
The regular expression pattern to search for within the provided\nvalue, or a pre-compiled regular expression. By default, raises a\nValidationError with message\nand code if a match is not found. That standard behavior can\nbe reversed by setting inverse_match to True, in which case\nthe ValidationError is raised when a\nmatch is found. By default, matches any string (including an empty\nstring).
The error message used by\nValidationError if validation fails.\nDefaults to "Enter a valid value".
The error code used by ValidationError\nif validation fails. Defaults to "invalid".
The match mode for regex. Defaults to False.
The flags used when compiling the regular expression string\nregex. If regex is a pre-compiled regular expression,\nand flags is overridden, TypeError is raised. Defaults\nto 0.
EmailValidatorLink to this heading#The error message used by\nValidationError if validation fails.\nDefaults to "Enter a valid email address".
The error code used by ValidationError\nif validation fails. Defaults to "invalid".
Whitelist of email domains to allow. By default, a regular expression\n(the domain_regex attribute) is used to validate whatever appears\nafter the @ sign. However, if that string appears in the whitelist, this\nvalidation is bypassed. If not provided, the default whitelist is\n['localhost']. Other domains that don’t contain a dot won’t pass\nvalidation, so you’d need to whitelist them as necessary.
URLValidatorLink to this heading#A RegexValidator that ensures a value looks like a URL, and raises\nan error code of 'invalid' if it doesn’t.
Loopback addresses and reserved IP spaces are considered valid. Literal\nIPv6 addresses (RFC 2732) and unicode domains are both supported.
\nIn addition to the optional arguments of its parent RegexValidator\nclass, URLValidator accepts an extra optional attribute:
URL/URI scheme list to validate against. If not provided, the default\nlist is ['http', 'https', 'ftp', 'ftps']. As a reference, the IANA\nwebsite provides a full list of valid URI schemes.
validate_emailLink to this heading#An EmailValidator instance without any customizations.
validate_slugLink to this heading#A RegexValidator instance that ensures a value consists of only\nletters, numbers, underscores or hyphens.
validate_unicode_slugLink to this heading#A RegexValidator instance that ensures a value consists of only\nUnicode letters, numbers, underscores, or hyphens.
validate_ipv4_addressLink to this heading#A RegexValidator instance that ensures a value looks like an IPv4\naddress.
validate_ipv6_addressLink to this heading#Uses django.utils.ipv6 to check the validity of an IPv6 address.
validate_ipv46_addressLink to this heading#Uses both validate_ipv4_address and validate_ipv6_address to\nensure a value is either a valid IPv4 or IPv6 address.
validate_comma_separated_integer_listLink to this heading#A RegexValidator instance that ensures a value is a\ncomma-separated list of integers.
int_list_validatorLink to this heading#Returns a RegexValidator instance that ensures a string consists\nof integers separated by sep. It allows negative integers when\nallow_negative is True.
MaxValueValidatorLink to this heading#Raises a ValidationError with a code of\n'max_value' if value is greater than limit_value.
MinValueValidatorLink to this heading#Raises a ValidationError with a code of\n'min_value' if value is less than limit_value.
MaxLengthValidatorLink to this heading#Raises a ValidationError with a code of\n'max_length' if the length of value is greater than limit_value.
MinLengthValidatorLink to this heading#Raises a ValidationError with a code of\n'min_length' if the length of value is less than limit_value.
DecimalValidatorLink to this heading#Raises ValidationError with the following\ncodes:
'max_digits' if the number of digits is larger than max_digits.
'max_decimal_places' if the number of decimals is larger than\ndecimal_places.
'max_whole_digits' if the number of whole digits is larger than\nthe difference between max_digits and decimal_places.
FileExtensionValidatorLink to this heading#Raises a ValidationError with a code of\n'invalid_extension' if the extension of value.name (value is\na File) isn’t found in allowed_extensions.\nThe extension is compared case-insensitively with allowed_extensions.
validate_image_file_extensionLink to this heading#Uses Pillow to ensure that value.name (value is a\nFile) has a valid image extension.
ProhibitNullCharactersValidatorLink to this heading#Raises a ValidationError if str(value)\ncontains one or more nulls characters ('\\x00').
The error message used by\nValidationError if validation fails.\nDefaults to "Null characters are not allowed.".
The error code used by ValidationError\nif validation fails. Defaults to "null_characters_not_allowed".