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
¶RegexValidator
(regex=None, message=None, code=None, inverse_match=None, flags=0)[source]¶Parameters: |
|
---|
regex
¶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).
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"
.
EmailValidator
¶EmailValidator
(message=None, code=None, whitelist=None)[source]¶Parameters: |
---|
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"
.
whitelist
¶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
¶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.
Loopback addresses and reserved IP spaces are considered valid. Literal IPv6 addresses (RFC 2732) 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.
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 by sep
. It allows negative integers when
allow_negative
is True
.
MaxValueValidator
¶MaxValueValidator
(limit_value, message=None)[source]¶Raises a ValidationError
with a code of
'max_value'
if value
is greater than limit_value
.
MinValueValidator
¶MinValueValidator
(limit_value, message=None)[source]¶Raises a ValidationError
with a code of
'min_value'
if value
is less than limit_value
.
MaxLengthValidator
¶MaxLengthValidator
(limit_value, message=None)[source]¶Raises a ValidationError
with a code of
'max_length'
if the length of value
is greater than limit_value
.
MinLengthValidator
¶MinLengthValidator
(limit_value, message=None)[source]¶Raises a ValidationError
with a code of
'min_length'
if the length of value
is less than limit_value
.
DecimalValidator
¶DecimalValidator
(max_digits, decimal_places)[source]¶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
¶FileExtensionValidator
(allowed_extensions, message, code)[source]¶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
¶validate_image_file_extension
[source]¶Uses Pillow to ensure that value.name
(value
is a
File
) has a valid image extension.
ProhibitNullCharactersValidator
¶ProhibitNullCharactersValidator
(message=None, code=None)[source]¶Raises a ValidationError
if str(value)
contains one or more nulls 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"
.
Dec 24, 2018