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.
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.
A RegexValidator searches the provided value for a given
regular expression with re.search(). By default, raises a
ValidationError with message and
code if a match is not found. Its behavior can be inverted by
setting inverse_match to True, in which case the
ValidationError is raised when a match
is found.
The regular expression pattern to search for within the provided
value, using re.search(). This may be a string or a
pre-compiled regular expression created with re.compile().
Defaults to the empty string, which will be found in every possible
value.
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¶An EmailValidator ensures that a value looks like an email, and
raises a ValidationError with
message and code if it doesn't. Values longer than 320
characters are always considered invalid.
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".
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 the allowlist,
this validation is bypassed. If not provided, the default allowlist
is ['localhost']. Other domains that don't contain a dot won't pass
validation, so you'd need to add them to the allowlist as
necessary.
URLValidator¶A RegexValidator subclass that ensures a value looks like a URL,
and raises an error code of 'invalid' if it doesn't. Values longer than
max_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:
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.
The maximum length of values that could be considered valid. Defaults to 2048 characters.
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.
MinValueValidator¶Raises a ValidationError with a code of
'min_value' if value is less than limit_value, which may 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.
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.
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 null 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".
StepValueValidator¶Raises a ValidationError with a code of
'step_size' if value is not an integral multiple of
limit_value, which can be a float, integer or decimal value or a
callable. When offset is set, the validation occurs against
limit_value plus offset. For example, for
StepValueValidator(3, offset=1.4) valid values include 1.4,
4.4, 7.4, 10.4, and so on.
The offset argument was added.
Jan 15, 2024