This document contains all the API references of Field including the
field options and field types Django offers.
Ver também
If the built-in fields don’t do the trick, you can try django-localflavor (documentation), which contains assorted pieces of code that are useful for particular countries and cultures.
Also, you can easily write your own custom model fields.
Nota
Technically, these models are defined in django.db.models.fields, but
for convenience they’re imported into django.db.models; the standard
convention is to use from django.db import models and refer to fields as
models.<Foo>Field.
The following arguments are available to all field types. All are optional.
null¶Field.null¶Se True, o Django irá usar valores “vazios” como NULL no banco de dados. Padrão is False.
Avoid using null on string-based fields such as
CharField and TextField. If a string-based field has
null=True, that means it has two possible values for “no data”: NULL,
and the empty string. In most cases, it’s redundant to have two possible values
for “no data;” the Django convention is to use the empty string, not
NULL. One exception is when a CharField has both unique=True
and blank=True set. In this situation, null=True is required to avoid
unique constraint violations when saving multiple objects with blank values.
For both string-based and non-string-based fields, you will also need to
set blank=True if you wish to permit empty values in forms, as the
null parameter only affects database storage
(see blank).
Nota
When using the Oracle database backend, the value NULL will be stored to
denote the empty string regardless of this attribute.
If you want to accept null values with BooleanField,
use NullBooleanField instead.
blank¶Field.blank¶Se True, é permitido o campo estar em “branco”. O padrão é False.
Note that this is different than null. null is
purely database-related, whereas blank is validation-related. If
a field has blank=True, form validation will allow entry of an empty value.
If a field has blank=False, the field will be required.
choices¶Field.choices¶An iterable (e.g., a list or tuple) consisting itself of iterables of exactly
two items (e.g. [(A, B), (A, B) ...]) to use as choices for this field. If
this is given, the default form widget will be a select box with these choices
instead of the standard text field.
The first element in each tuple is the actual value to be set on the model, and the second element is the human-readable name. For example:
YEAR_IN_SCHOOL_CHOICES = (
('FR', 'Freshman'),
('SO', 'Sophomore'),
('JR', 'Junior'),
('SR', 'Senior'),
)
Generally, it’s best to define choices inside a model class, and to define a suitably-named constant for each value:
from django.db import models
class Student(models.Model):
FRESHMAN = 'FR'
SOPHOMORE = 'SO'
JUNIOR = 'JR'
SENIOR = 'SR'
YEAR_IN_SCHOOL_CHOICES = (
(FRESHMAN, 'Freshman'),
(SOPHOMORE, 'Sophomore'),
(JUNIOR, 'Junior'),
(SENIOR, 'Senior'),
)
year_in_school = models.CharField(
max_length=2,
choices=YEAR_IN_SCHOOL_CHOICES,
default=FRESHMAN,
)
def is_upperclass(self):
return self.year_in_school in (self.JUNIOR, self.SENIOR)
Though you can define a choices list outside of a model class and then
refer to it, defining the choices and names for each choice inside the
model class keeps all of that information with the class that uses it,
and makes the choices easy to reference (e.g, Student.SOPHOMORE
will work anywhere that the Student model has been imported).
You can also collect your available choices into named groups that can be used for organizational purposes:
MEDIA_CHOICES = (
('Audio', (
('vinyl', 'Vinyl'),
('cd', 'CD'),
)
),
('Video', (
('vhs', 'VHS Tape'),
('dvd', 'DVD'),
)
),
('unknown', 'Unknown'),
)
The first element in each tuple is the name to apply to the group. The second element is an iterable of 2-tuples, with each 2-tuple containing a value and a human-readable name for an option. Grouped options may be combined with ungrouped options within a single list (such as the unknown option in this example).
For each model field that has choices set, Django will add a
method to retrieve the human-readable name for the field’s current value. See
get_FOO_display() in the database API
documentation.
Note that choices can be any iterable object – not necessarily a list or tuple.
This lets you construct choices dynamically. But if you find yourself hacking
choices to be dynamic, you’re probably better off using a proper
database table with a ForeignKey. choices is meant for
static data that doesn’t change much, if ever.
Unless blank=False is set on the field along with a
default then a label containing "---------" will be rendered
with the select box. To override this behavior, add a tuple to choices
containing None; e.g. (None, 'Your String For Display').
Alternatively, you can use an empty string instead of None where this makes
sense - such as on a CharField.
db_column¶Field.db_column¶The name of the database column to use for this field. If this isn’t given, Django will use the field’s name.
If your database column name is an SQL reserved word, or contains characters that aren’t allowed in Python variable names – notably, the hyphen – that’s OK. Django quotes column and table names behind the scenes.
db_tablespace¶Field.db_tablespace¶The name of the database tablespace to use for
this field’s index, if this field is indexed. The default is the project’s
DEFAULT_INDEX_TABLESPACE setting, if set, or the
db_tablespace of the model, if any. If the backend doesn’t
support tablespaces for indexes, this option is ignored.
default¶Field.default¶O valor padrão para o campo. Este pode ser um valor ou um objeto “callable”. Se “callable” ele será chamado cada vez que um novo objeto for criado.
The default can’t be a mutable object (model instance, list, set, etc.),
as a reference to the same instance of that object would be used as the default
value in all new model instances. Instead, wrap the desired default in a
callable. For example, if you want to specify a default dict for
JSONField, use a function:
def contact_default():
return {"email": "to1@example.com"}
contact_info = JSONField("ContactInfo", default=contact_default)
lambdas can’t be used for field options like default because they
can’t be serialized by migrations. See that
documentation for other caveats.
For fields like ForeignKey that map to model instances, defaults
should be the value of the field they reference (pk unless
to_field is set) instead of model instances.
The default value is used when new model instances are created and a value
isn’t provided for the field. When the field is a primary key, the default is
also used when the field is set to None.
editable¶Field.editable¶If False, the field will not be displayed in the admin or any other
ModelForm. They are also skipped during model
validation. Default is True.
error_messages¶Field.error_messages¶The error_messages argument lets you override the default messages that the
field will raise. Pass in a dictionary with keys matching the error messages you
want to override.
Error message keys include null, blank, invalid, invalid_choice,
unique, and unique_for_date. Additional error message keys are
specified for each field in the Field types section below.
These error messages often don’t propagate to forms. See Considerations regarding model’s error_messages.
help_text¶Field.help_text¶Texto extra de ajuda para ser mostrado com o “widget” do formulário. É útil para documentar mesmo que seu campo não seja usado em um formulário.
Note that this value is not HTML-escaped in automatically-generated
forms. This lets you include HTML in help_text if you so
desire. For example:
help_text="Please use the following format: <em>YYYY-MM-DD</em>."
Alternatively you can use plain text and
django.utils.html.escape() to escape any HTML special characters. Ensure
that you escape any help text that may come from untrusted users to avoid a
cross-site scripting attack.
primary_key¶Field.primary_key¶Se True, este campo será a chave-primária do seu modelo.
If you don’t specify primary_key=True for any field in your model, Django
will automatically add an AutoField to hold the primary key, so you
don’t need to set primary_key=True on any of your fields unless you want to
override the default primary-key behavior. For more, see
Campos chave-primária automáticos..
primary_key=True implies null=False and
unique=True. Only one primary key is allowed on an
object.
The primary key field is read-only. If you change the value of the primary key on an existing object and then save it, a new object will be created alongside the old one.
unique¶Field.unique¶Se True, este campo deve ser único dentro da tabela
This is enforced at the database level and by model validation. If
you try to save a model with a duplicate value in a unique
field, a django.db.IntegrityError will be raised by the model’s
save() method.
This option is valid on all field types except ManyToManyField and
OneToOneField.
Note that when unique is True, you don’t need to specify
db_index, because unique implies the creation of an index.
In older versions, unique=True can’t be used on FileField.
unique_for_date¶Field.unique_for_date¶Set this to the name of a DateField or DateTimeField to
require that this field be unique for the value of the date field.
For example, if you have a field title that has
unique_for_date="pub_date", then Django wouldn’t allow the entry of two
records with the same title and pub_date.
Note that if you set this to point to a DateTimeField, only the date
portion of the field will be considered. Besides, when USE_TZ is
True, the check will be performed in the current time zone at the time the object gets saved.
This is enforced by Model.validate_unique() during model validation
but not at the database level. If any unique_for_date constraint
involves fields that are not part of a ModelForm (for
example, if one of the fields is listed in exclude or has
editable=False), Model.validate_unique() will
skip validation for that particular constraint.
unique_for_month¶Field.unique_for_month¶Like unique_for_date, but requires the field to be unique with
respect to the month.
verbose_name¶Field.verbose_name¶A human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces. See Verbose field names.
validators¶Field.validators¶A list of validators to run for this field. See the validators documentation for more information.
Field implements the lookup registration API.
The API can be used to customize which lookups are available for a field class, and
how lookups are fetched from a field.
AutoField¶AutoField(**options)[código fonte]¶An IntegerField that automatically increments
according to available IDs. You usually won’t need to use this directly; a
primary key field will automatically be added to your model if you don’t specify
otherwise. See Campos chave-primária automáticos..
BigAutoField¶BigAutoField(**options)[código fonte]¶A 64-bit integer, much like an AutoField except that it is
guaranteed to fit numbers from 1 to 9223372036854775807.
BigIntegerField¶BigIntegerField(**options)[código fonte]¶A 64-bit integer, much like an IntegerField except that it is
guaranteed to fit numbers from -9223372036854775808 to
9223372036854775807. The default form widget for this field is a
TextInput.
BinaryField¶BinaryField(**options)[código fonte]¶A field to store raw binary data. It only supports bytes assignment. Be
aware that this field has limited functionality. For example, it is not possible
to filter a queryset on a BinaryField value. It is also not possible to
include a BinaryField in a ModelForm.
Abusing BinaryField
Although you might think about storing files in the database, consider that it is bad design in 99% of the cases. This field is not a replacement for proper static files handling.
BooleanField¶BooleanField(**options)[código fonte]¶A true/false field.
The default form widget for this field is a
CheckboxInput.
If you need to accept null values then use
NullBooleanField instead.
The default value of BooleanField is None when Field.default
isn’t defined.
CharField¶CharField(max_length=None, **options)[código fonte]¶A string field, for small- to large-sized strings.
For large amounts of text, use TextField.
The default form widget for this field is a TextInput.
CharField has one extra required argument:
CharField.max_length¶The maximum length (in characters) of the field. The max_length is enforced at the database level and in Django’s validation.
Nota
If you are writing an application that must be portable to multiple
database backends, you should be aware that there are restrictions on
max_length for some backends. Refer to the database backend
notes for details.
DateField¶DateField(auto_now=False, auto_now_add=False, **options)[código fonte]¶A date, represented in Python by a datetime.date instance. Has a few extra,
optional arguments:
DateField.auto_now¶Automatically set the field to now every time the object is saved. Useful for “last-modified” timestamps. Note that the current date is always used; it’s not just a default value that you can override.
The field is only automatically updated when calling Model.save(). The field isn’t updated when making updates
to other fields in other ways such as QuerySet.update(), though you can specify a custom
value for the field in an update like that.
DateField.auto_now_add¶Automatically set the field to now when the object is first created. Useful
for creation of timestamps. Note that the current date is always used;
it’s not just a default value that you can override. So even if you
set a value for this field when creating the object, it will be ignored.
If you want to be able to modify this field, set the following instead of
auto_now_add=True:
DateField: default=date.today - from
datetime.date.today()DateTimeField: default=timezone.now - from
django.utils.timezone.now()The default form widget for this field is a
TextInput. The admin adds a JavaScript calendar,
and a shortcut for “Today”. Includes an additional invalid_date error
message key.
The options auto_now_add, auto_now, and default are mutually exclusive.
Any combination of these options will result in an error.
Nota
As currently implemented, setting auto_now or auto_now_add to
True will cause the field to have editable=False and blank=True
set.
Nota
The auto_now and auto_now_add options will always use the date in
the default timezone at the moment of
creation or update. If you need something different, you may want to
consider simply using your own callable default or overriding save()
instead of using auto_now or auto_now_add; or using a
DateTimeField instead of a DateField and deciding how to handle the
conversion from datetime to date at display time.
DateTimeField¶DateTimeField(auto_now=False, auto_now_add=False, **options)[código fonte]¶A date and time, represented in Python by a datetime.datetime instance.
Takes the same extra arguments as DateField.
The default form widget for this field is a single
TextInput. The admin uses two separate
TextInput widgets with JavaScript shortcuts.
DecimalField¶DecimalField(max_digits=None, decimal_places=None, **options)[código fonte]¶A fixed-precision decimal number, represented in Python by a
Decimal instance. Has two required arguments:
DecimalField.max_digits¶The maximum number of digits allowed in the number. Note that this number
must be greater than or equal to decimal_places.
DecimalField.decimal_places¶The number of decimal places to store with the number.
For example, to store numbers up to 999 with a resolution of 2 decimal
places, you’d use:
models.DecimalField(..., max_digits=5, decimal_places=2)
And to store numbers up to approximately one billion with a resolution of 10 decimal places:
models.DecimalField(..., max_digits=19, decimal_places=10)
The default form widget for this field is a NumberInput
when localize is False or
TextInput otherwise.
Nota
For more information about the differences between the
FloatField and DecimalField classes, please
see FloatField vs. DecimalField.
DurationField¶DurationField(**options)[código fonte]¶A field for storing periods of time - modeled in Python by
timedelta. When used on PostgreSQL, the data type
used is an interval and on Oracle the data type is INTERVAL DAY(9) TO
SECOND(6). Otherwise a bigint of microseconds is used.
Nota
Arithmetic with DurationField works in most cases. However on all
databases other than PostgreSQL, comparing the value of a DurationField
to arithmetic on DateTimeField instances will not work as expected.
EmailField¶EmailField(max_length=254, **options)[código fonte]¶A CharField that checks that the value is a valid email address. It
uses EmailValidator to validate the input.
FileField¶FileField(upload_to=None, max_length=100, **options)[código fonte]¶A file-upload field.
Nota
The primary_key argument isn’t supported and will raise a an error if
used.
Has two optional arguments:
FileField.upload_to¶This attribute provides a way of setting the upload directory and file name,
and can be set in two ways. In both cases, the value is passed to the
Storage.save() method.
If you specify a string value, it may contain strftime()
formatting, which will be replaced by the date/time of the file upload (so
that uploaded files don’t fill up the given directory). For example:
class MyModel(models.Model):
# file will be uploaded to MEDIA_ROOT/uploads
upload = models.FileField(upload_to='uploads/')
# or...
# file will be saved to MEDIA_ROOT/uploads/2015/01/30
upload = models.FileField(upload_to='uploads/%Y/%m/%d/')
If you are using the default
FileSystemStorage, the string value
will be appended to your MEDIA_ROOT path to form the location on
the local filesystem where uploaded files will be stored. If you are using
a different storage, check that storage’s documentation to see how it
handles upload_to.
upload_to may also be a callable, such as a function. This will be
called to obtain the upload path, including the filename. This callable must
accept two arguments and return a Unix-style path (with forward slashes)
to be passed along to the storage system. The two arguments are:
| Argument | Descrição |
|---|---|
instance |
An instance of the model where the
In most cases, this object will not have been
saved to the database yet, so if it uses the
default |
filename |
The filename that was originally given to the file. This may or may not be taken into account when determining the final destination path. |
Por exemplo:
def user_directory_path(instance, filename):
# file will be uploaded to MEDIA_ROOT/user_<id>/<filename>
return 'user_{0}/{1}'.format(instance.user.id, filename)
class MyModel(models.Model):
upload = models.FileField(upload_to=user_directory_path)
FileField.storage¶A storage object, which handles the storage and retrieval of your files. See Managing files for details on how to provide this object.
The default form widget for this field is a
ClearableFileInput.
Using a FileField or an ImageField (see below) in a model
takes a few steps:
MEDIA_ROOT com o caminho completo para o diretório onde você gostaria que o Django fizesse o upload de seus arquivos. (Para performance, esses arquivos não são armazenados no banco de dados.) Define MEDIA_URL como a URL pública desse diretório. Tenha certeza que esse diretório seja gravável pelo usuário da conta referente ao servidor Web.FileField or ImageField to your model, defining
the upload_to option to specify a subdirectory of
MEDIA_ROOT to use for uploaded files.MEDIA_ROOT). You’ll most likely want to use the
convenience url attribute
provided by Django. For example, if your ImageField is called
mug_shot, you can get the absolute path to your image in a template with
{{ object.mug_shot.url }}.For example, say your MEDIA_ROOT is set to '/home/media', and
upload_to is set to 'photos/%Y/%m/%d'. The '%Y/%m/%d'
part of upload_to is strftime() formatting;
'%Y' is the four-digit year, '%m' is the two-digit month and '%d' is
the two-digit day. If you upload a file on Jan. 15, 2007, it will be saved in
the directory /home/media/photos/2007/01/15.
If you wanted to retrieve the uploaded file’s on-disk filename, or the file’s
size, you could use the name and
size attributes respectively; for more
information on the available attributes and methods, see the
File class reference and the Managing files
topic guide.
Nota
The file is saved as part of saving the model in the database, so the actual file name used on disk cannot be relied on until after the model has been saved.
The uploaded file’s relative URL can be obtained using the
url attribute. Internally,
this calls the url() method of the
underlying Storage class.
Note that whenever you deal with uploaded files, you should pay close attention to where you’re uploading them and what type of files they are, to avoid security holes. Validate all uploaded files so that you’re sure the files are what you think they are. For example, if you blindly let somebody upload files, without validation, to a directory that’s within your Web server’s document root, then somebody could upload a CGI or PHP script and execute that script by visiting its URL on your site. Don’t allow that.
Also note that even an uploaded HTML file, since it can be executed by the browser (though not by the server), can pose security threats that are equivalent to XSS or CSRF attacks.
FileField instances are created in your database as varchar
columns with a default max length of 100 characters. As with other fields, you
can change the maximum length using the max_length argument.
FileField and FieldFile¶FieldFile[código fonte]¶When you access a FileField on a model, you are
given an instance of FieldFile as a proxy for accessing the underlying
file.
The API of FieldFile mirrors that of File,
with one key difference: The object wrapped by the class is not necessarily a
wrapper around Python’s built-in file object. Instead, it is a wrapper around
the result of the Storage.open()
method, which may be a File object, or it may be a
custom storage’s implementation of the File API.
In addition to the API inherited from File such as
read() and write(), FieldFile includes several methods that
can be used to interact with the underlying file:
Aviso
Two methods of this class, save() and
delete(), default to saving the model object of the
associated FieldFile in the database.
FieldFile.name¶The name of the file including the relative path from the root of the
Storage of the associated
FileField.
FieldFile.size¶The result of the underlying Storage.size() method.
FieldFile.url¶A read-only property to access the file’s relative URL by calling the
url() method of the underlying
Storage class.
FieldFile.open(mode='rb')[código fonte]¶Opens or reopens the file associated with this instance in the specified
mode. Unlike the standard Python open() method, it doesn’t return a
file descriptor.
Since the underlying file is opened implicitly when accessing it, it may be
unnecessary to call this method except to reset the pointer to the underlying
file or to change the mode.
FieldFile.close()[código fonte]¶Behaves like the standard Python file.close() method and closes the file
associated with this instance.
FieldFile.save(name, content, save=True)[código fonte]¶This method takes a filename and file contents and passes them to the storage
class for the field, then associates the stored file with the model field.
If you want to manually associate file data with
FileField instances on your model, the save()
method is used to persist that file data.
Takes two required arguments: name which is the name of the file, and
content which is an object containing the file’s contents. The
optional save argument controls whether or not the model instance is
saved after the file associated with this field has been altered. Defaults to
True.
Note that the content argument should be an instance of
django.core.files.File, not Python’s built-in file object.
You can construct a File from an existing
Python file object like this:
from django.core.files import File
# Open an existing file using Python's built-in open()
f = open('/path/to/hello.world')
myfile = File(f)
Or you can construct one from a Python string like this:
from django.core.files.base import ContentFile
myfile = ContentFile("hello world")
For more information, see Managing files.
FieldFile.delete(save=True)[código fonte]¶Deletes the file associated with this instance and clears all attributes on
the field. Note: This method will close the file if it happens to be open when
delete() is called.
The optional save argument controls whether or not the model instance is
saved after the file associated with this field has been deleted. Defaults to
True.
Note that when a model is deleted, related files are not deleted. If you need to cleanup orphaned files, you’ll need to handle it yourself (for instance, with a custom management command that can be run manually or scheduled to run periodically via e.g. cron).
FilePathField¶FilePathField(path=None, match=None, recursive=False, max_length=100, **options)[código fonte]¶A CharField whose choices are limited to the filenames in a certain
directory on the filesystem. Has three special arguments, of which the first is
required:
FilePathField.path¶Required. The absolute filesystem path to a directory from which this
FilePathField should get its choices. Example: "/home/images".
FilePathField.match¶Optional. A regular expression, as a string, that FilePathField
will use to filter filenames. Note that the regex will be applied to the
base filename, not the full path. Example: "foo.*\.txt$", which will
match a file called foo23.txt but not bar.txt or foo23.png.
FilePathField.recursive¶Optional. Either True or False. Default is False. Specifies
whether all subdirectories of path should be included
FilePathField.allow_files¶Optional. Either True or False. Default is True. Specifies
whether files in the specified location should be included. Either this or
allow_folders must be True.
FilePathField.allow_folders¶Optional. Either True or False. Default is False. Specifies
whether folders in the specified location should be included. Either this
or allow_files must be True.
Of course, these arguments can be used together.
The one potential gotcha is that match applies to the
base filename, not the full path. So, this example:
FilePathField(path="/home/images", match="foo.*", recursive=True)
…will match /home/images/foo.png but not /home/images/foo/bar.png
because the match applies to the base filename
(foo.png and bar.png).
FilePathField instances are created in your database as varchar
columns with a default max length of 100 characters. As with other fields, you
can change the maximum length using the max_length argument.
FloatField¶FloatField(**options)[código fonte]¶A floating-point number represented in Python by a float instance.
The default form widget for this field is a NumberInput
when localize is False or
TextInput otherwise.
FloatField vs. DecimalField
The FloatField class is sometimes mixed up with the
DecimalField class. Although they both represent real numbers, they
represent those numbers differently. FloatField uses Python’s float
type internally, while DecimalField uses Python’s Decimal type. For
information on the difference between the two, see Python’s documentation
for the decimal module.
ImageField¶ImageField(upload_to=None, height_field=None, width_field=None, max_length=100, **options)[código fonte]¶Inherits all attributes and methods from FileField, but also
validates that the uploaded object is a valid image.
In addition to the special attributes that are available for FileField,
an ImageField also has height and width attributes.
To facilitate querying on those attributes, ImageField has two extra
optional arguments:
ImageField.height_field¶Name of a model field which will be auto-populated with the height of the image each time the model instance is saved.
ImageField.width_field¶Name of a model field which will be auto-populated with the width of the image each time the model instance is saved.
Requires the Pillow library.
ImageField instances are created in your database as varchar
columns with a default max length of 100 characters. As with other fields, you
can change the maximum length using the max_length argument.
The default form widget for this field is a
ClearableFileInput.
IntegerField¶IntegerField(**options)[código fonte]¶An integer. Values from -2147483648 to 2147483647 are safe in all
databases supported by Django. The default form widget for this field is a
NumberInput when localize
is False or TextInput otherwise.
GenericIPAddressField¶GenericIPAddressField(protocol='both', unpack_ipv4=False, **options)[código fonte]¶An IPv4 or IPv6 address, in string format (e.g. 192.0.2.30 or
2a02:42fe::4). The default form widget for this field is a
TextInput.
The IPv6 address normalization follows RFC 4291#section-2.2 section 2.2,
including using the IPv4 format suggested in paragraph 3 of that section, like
::ffff:192.0.2.0. For example, 2001:0::0:01 would be normalized to
2001::1, and ::ffff:0a0a:0a0a to ::ffff:10.10.10.10. All characters
are converted to lowercase.
GenericIPAddressField.protocol¶Limits valid inputs to the specified protocol.
Accepted values are 'both' (default), 'IPv4'
or 'IPv6'. Matching is case insensitive.
GenericIPAddressField.unpack_ipv4¶Unpacks IPv4 mapped addresses like ::ffff:192.0.2.1.
If this option is enabled that address would be unpacked to
192.0.2.1. Default is disabled. Can only be used
when protocol is set to 'both'.
If you allow for blank values, you have to allow for null values since blank values are stored as null.
NullBooleanField¶NullBooleanField(**options)[código fonte]¶Like a BooleanField, but allows NULL as one of the options. Use
this instead of a BooleanField with null=True. The default form
widget for this field is a NullBooleanSelect.
PositiveIntegerField¶PositiveIntegerField(**options)[código fonte]¶Like an IntegerField, but must be either positive or zero (0).
Values from 0 to 2147483647 are safe in all databases supported by
Django. The value 0 is accepted for backward compatibility reasons.
PositiveSmallIntegerField¶PositiveSmallIntegerField(**options)[código fonte]¶Like a PositiveIntegerField, but only allows values under a certain
(database-dependent) point. Values from 0 to 32767 are safe in all
databases supported by Django.
SlugField¶SlugField(max_length=50, **options)[código fonte]¶Slug is a newspaper term. A slug is a short label for something, containing only letters, numbers, underscores or hyphens. They’re generally used in URLs.
Like a CharField, you can specify max_length (read the note
about database portability and max_length in that section,
too). If max_length is not specified, Django will use a
default length of 50.
Implies setting Field.db_index to True.
It is often useful to automatically prepopulate a SlugField based on the value
of some other value. You can do this automatically in the admin using
prepopulated_fields.
SlugField.allow_unicode¶If True, the field accepts Unicode letters in addition to ASCII
letters. Defaults to False.
SmallIntegerField¶SmallIntegerField(**options)[código fonte]¶Like an IntegerField, but only allows values under a certain
(database-dependent) point. Values from -32768 to 32767 are safe in all
databases supported by Django.
TextField¶TextField(**options)[código fonte]¶A large text field. The default form widget for this field is a
Textarea.
If you specify a max_length attribute, it will be reflected in the
Textarea widget of the auto-generated form field.
However it is not enforced at the model or database level. Use a
CharField for that.
TimeField¶TimeField(auto_now=False, auto_now_add=False, **options)[código fonte]¶A time, represented in Python by a datetime.time instance. Accepts the same
auto-population options as DateField.
The default form widget for this field is a TextInput.
The admin adds some JavaScript shortcuts.
URLField¶URLField(max_length=200, **options)[código fonte]¶A CharField for a URL.
The default form widget for this field is a TextInput.
Like all CharField subclasses, URLField takes the optional
max_length argument. If you don’t specify
max_length, a default of 200 is used.
UUIDField¶UUIDField(**options)[código fonte]¶A field for storing universally unique identifiers. Uses Python’s
UUID class. When used on PostgreSQL, this stores in a
uuid datatype, otherwise in a char(32).
Universally unique identifiers are a good alternative to AutoField for
primary_key. The database will not generate the UUID for you, so
it is recommended to use default:
import uuid
from django.db import models
class MyUUIDModel(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
# other fields
Note that a callable (with the parentheses omitted) is passed to default,
not an instance of UUID.
Field[código fonte]¶Field is an abstract class that represents a database table column.
Django uses fields to create the database table (db_type()), to map
Python types to database (get_prep_value()) and vice-versa
(from_db_value()).
A field is thus a fundamental piece in different Django APIs, notably,
models and querysets.
In models, a field is instantiated as a class attribute and represents a
particular table column, see Models. It has attributes
such as null and unique, and methods that Django uses to
map the field value to database-specific values.
A Field is a subclass of
RegisterLookupMixin and thus both
Transform and
Lookup can be registered on it to be used
in QuerySets (e.g. field_name__exact="foo"). All built-in
lookups are registered by default.
All of Django’s built-in fields, such as CharField, are particular
implementations of Field. If you need a custom field, you can either
subclass any of the built-in fields or write a Field from scratch. In
either case, see Escrevendo campos personalizados de modelos..
description¶A verbose description of the field, e.g. for the
django.contrib.admindocs application.
The description can be of the form:
description = _("String (up to %(max_length)s)")
where the arguments are interpolated from the field’s __dict__.
To map a Field to a database-specific type, Django exposes several
methods:
get_internal_type()[código fonte]¶Returns a string naming this field for backend specific purposes. By default, it returns the class name.
Veja Emulando tipos de campos internos. para uso em campos personalizados.
db_type(connection)[código fonte]¶Returns the database column data type for the Field, taking
into account the connection.
Veja Tipos de banco de dados personalizados para uso em campos customizados.
rel_db_type(connection)[código fonte]¶Returns the database column data type for fields such as ForeignKey
and OneToOneField that point to the Field, taking
into account the connection.
Veja Tipos de banco de dados personalizados para uso em campos customizados.
There are three main situations where Django needs to interact with the database backend and fields:
When querying, get_db_prep_value() and get_prep_value() are used:
get_prep_value(value)[código fonte]¶value is the current value of the model’s attribute, and the method
should return data in a format that has been prepared for use as a
parameter in a query.
Veja Convertendo objetos Python para valores em queries para uso.
get_db_prep_value(value, connection, prepared=False)[código fonte]¶Converts value to a backend-specific value. By default it returns
value if prepared=True and get_prep_value() if is
False.
See Convertendo valores de queries para valores de banco de dados for usage.
Quando os dados são carregados, from_db_value() é usado:
from_db_value(value, expression, connection)¶Converts a value as returned by the database to a Python object. It is
the reverse of get_prep_value().
This method is not used for most built-in fields as the database backend already returns the correct Python type, or the backend itself does the conversion.
See Convertendo valores para objetos Python for usage.
Nota
For performance reasons, from_db_value is not implemented as a
no-op on fields which do not require it (all Django fields).
Consequently you may not call super in your definition.
Quando salva, pre_save() and get_db_prep_save() é utilizado:
get_db_prep_save(value, connection)[código fonte]¶Same as the get_db_prep_value(), but called when the field value
must be saved to the database. By default returns
get_db_prep_value().
pre_save(model_instance, add)[código fonte]¶Method called prior to get_db_prep_save() to prepare the value
before being saved (e.g. for DateField.auto_now).
model_instance is the instance this field belongs to and add
is whether the instance is being saved to the database for the first
time.
It should return the value of the appropriate attribute from
model_instance for this field. The attribute name is in
self.attname (this is set up by Field).
Veja Processando valores antes de salvar para usabilidade.
Fields often receive their values as a different type, either from serialization or from forms.
to_python(value)[código fonte]¶Converts the value into the correct Python object. It acts as the
reverse of value_to_string(), and is also called in
clean().
See Convertendo valores para objetos Python for usage.
Besides saving to the database, the field also needs to know how to serialize its value:
value_to_string(obj)[código fonte]¶Converts obj to a string. Used to serialize the value of the field.
Veja Convertendo dado do campo para serialização para usabilidade.
When using model forms, the Field
needs to know which form field it should be represented by:
formfield(form_class=None, choices_form_class=None, **kwargs)[código fonte]¶Returns the default django.forms.Field of this field for
ModelForm.
By default, if both form_class and choices_form_class are
None, it uses CharField. If the field has
choices and choices_form_class
isn’t specified, it uses TypedChoiceField.
See Especificando o campo de um formulário para o campo de um modelo. for usage.
deconstruct()[código fonte]¶Returns a 4-tuple with enough information to recreate the field:
"django.db.models.IntegerField").
This should be the most portable version, so less specific may be better.This method must be added to fields prior to 1.7 to migrate its data using Migrations.
Every Field instance contains several attributes that allow
introspecting its behavior. Use these attributes instead of isinstance
checks when you need to write code that depends on a field’s functionality.
These attributes can be used together with the Model._meta API to narrow down a search for specific field types.
Custom model fields should implement these flags.
Field.auto_created¶Boolean flag that indicates if the field was automatically created, such
as the OneToOneField used by model inheritance.
Field.concrete¶Boolean flag that indicates if the field has a database column associated with it.
Boolean flag that indicates if a field is used to back another non-hidden
field’s functionality (e.g. the content_type and object_id fields
that make up a GenericForeignKey). The hidden flag is used to
distinguish what constitutes the public subset of fields on the model from
all the fields on the model.
Nota
Options.get_fields()
excludes hidden fields by default. Pass in include_hidden=True to
return hidden fields in the results.
Field.is_relation¶Boolean flag that indicates if a field contains references to one or
more other models for its functionality (e.g. ForeignKey,
ManyToManyField, OneToOneField, etc.).
Field.model¶Returns the model on which the field is defined. If a field is defined on
a superclass of a model, model will refer to the superclass, not the
class of the instance.
These attributes are used to query for the cardinality and other details of a
relation. These attribute are present on all fields; however, they will only
have boolean values (rather than None) if the field is a relation type
(Field.is_relation=True).
Field.many_to_many¶Boolean flag that is True if the field has a many-to-many relation;
False otherwise. The only field included with Django where this is
True is ManyToManyField.
Field.many_to_one¶Boolean flag that is True if the field has a many-to-one relation, such
as a ForeignKey; False otherwise.
Field.one_to_many¶Boolean flag that is True if the field has a one-to-many relation, such
as a GenericRelation or the reverse of a ForeignKey; False
otherwise.
Field.one_to_one¶Boolean flag that is True if the field has a one-to-one relation, such
as a OneToOneField; False otherwise.
Points to the model the field relates to. For example, Author in
ForeignKey(Author, on_delete=models.CASCADE). The related_model for
a GenericForeignKey is always None.
ago 01, 2018