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fields.txt
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=====================
Model field reference
=====================
.. module:: django.db.models.fields
:synopsis: Built-in field types.
.. currentmodule:: django.db.models
This document contains all the API references of :class:`Field` including the
`field options`_ and `field types`_ Django offers.
.. seealso::
If the built-in fields don't do the trick, you can try `django-localflavor
<https://github.com/django/django-localflavor>`_ (`documentation
<https://django-localflavor.readthedocs.org/>`_), which contains assorted
pieces of code that are useful for particular countries and cultures.
Also, you can easily :doc:`write your own custom model fields
</howto/custom-model-fields>`.
.. note::
Technically, these models are defined in :mod:`django.db.models.fields`, but
for convenience they're imported into :mod:`django.db.models`; the standard
convention is to use ``from django.db import models`` and refer to fields as
``models.<Foo>Field``.
.. _common-model-field-options:
Field options
=============
The following arguments are available to all field types. All are optional.
``null``
--------
.. attribute:: Field.null
If ``True``, Django will store empty values as ``NULL`` in the database. Default
is ``False``.
Avoid using :attr:`~Field.null` on string-based fields such as
:class:`CharField` and :class:`TextField` because empty string values will
always be stored as empty strings, not as ``NULL``. 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``.
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
:attr:`~Field.null` parameter only affects database storage
(see :attr:`~Field.blank`).
.. note::
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 :attr:`~Field.null` values with :class:`BooleanField`,
use :class:`NullBooleanField` instead.
``blank``
---------
.. attribute:: Field.blank
If ``True``, the field is allowed to be blank. Default is ``False``.
Note that this is different than :attr:`~Field.null`. :attr:`~Field.null` is
purely database-related, whereas :attr:`~Field.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.
.. _field-choices:
``choices``
-----------
.. attribute:: 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 :attr:`~Field.choices` set, Django will add a
method to retrieve the human-readable name for the field's current value. See
:meth:`~django.db.models.Model.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
:attr:`~Field.choices` to be dynamic, you're probably better off using a proper
database table with a :class:`ForeignKey`. :attr:`~Field.choices` is meant for
static data that doesn't change much, if ever.
Unless :attr:`blank=False<Field.blank>` is set on the field along with a
:attr:`~Field.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 :class:`~django.db.models.CharField`.
``db_column``
-------------
.. attribute:: 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_index``
------------
.. attribute:: Field.db_index
If ``True``, a database index will be created for this field.
``db_tablespace``
-----------------
.. attribute:: Field.db_tablespace
The name of the :doc:`database tablespace </topics/db/tablespaces>` to use for
this field's index, if this field is indexed. The default is the project's
:setting:`DEFAULT_INDEX_TABLESPACE` setting, if set, or the
:attr:`~Options.db_tablespace` of the model, if any. If the backend doesn't
support tablespaces for indexes, this option is ignored.
``default``
-----------
.. attribute:: Field.default
The default value for the field. This can be a value or a callable object. If
callable it will be called every time a new object is created.
The default cannot 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 had a custom ``JSONField`` and wanted to specify
a dictionary as the default, use a function as follows::
def contact_default():
return {"email": "to1@example.com"}
contact_info = JSONField("ContactInfo", default=contact_default)
Note that ``lambda``\s cannot be used for field options like ``default``
because they cannot be :ref:`serialized by migrations <migration-serializing>`.
See that documentation for other caveats.
For fields like :class:`ForeignKey` that map to model instances, defaults
should be the value of the field they reference (``pk`` unless
:attr:`~ForeignKey.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``.
.. versionchanged:: 1.8
The default wasn't used for ``None`` primary key values in previous
versions.
``editable``
------------
.. attribute:: Field.editable
If ``False``, the field will not be displayed in the admin or any other
:class:`~django.forms.ModelForm`. They are also skipped during :ref:`model
validation <validating-objects>`. Default is ``True``.
``error_messages``
------------------
.. attribute:: 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.
``help_text``
-------------
.. attribute:: Field.help_text
Extra "help" text to be displayed with the form widget. It's useful for
documentation even if your field isn't used on a form.
Note that this value is *not* HTML-escaped in automatically-generated
forms. This lets you include HTML in :attr:`~Field.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``
---------------
.. attribute:: Field.primary_key
If ``True``, this field is the primary key for the model.
If you don't specify ``primary_key=True`` for any field in your model, Django
will automatically add an :class:`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
:ref:`automatic-primary-key-fields`.
``primary_key=True`` implies :attr:`null=False <Field.null>` and
:attr:`unique=True <Field.unique>`. 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``
----------
.. attribute:: Field.unique
If ``True``, this field must be unique throughout the table.
This is enforced at the database level and by model validation. If
you try to save a model with a duplicate value in a :attr:`~Field.unique`
field, a :exc:`django.db.IntegrityError` will be raised by the model's
:meth:`~django.db.models.Model.save` method.
This option is valid on all field types except :class:`ManyToManyField`,
:class:`OneToOneField`, and :class:`FileField`.
Note that when ``unique`` is ``True``, you don't need to specify
:attr:`~Field.db_index`, because ``unique`` implies the creation of an index.
``unique_for_date``
-------------------
.. attribute:: Field.unique_for_date
Set this to the name of a :class:`DateField` or :class:`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 :class:`DateTimeField`, only the date
portion of the field will be considered. Besides, when :setting:`USE_TZ` is
``True``, the check will be performed in the :ref:`current time zone
<default-current-time-zone>` at the time the object gets saved.
This is enforced by :meth:`Model.validate_unique()` during model validation
but not at the database level. If any :attr:`~Field.unique_for_date` constraint
involves fields that are not part of a :class:`~django.forms.ModelForm` (for
example, if one of the fields is listed in ``exclude`` or has
:attr:`editable=False<Field.editable>`), :meth:`Model.validate_unique()` will
skip validation for that particular constraint.
``unique_for_month``
--------------------
.. attribute:: Field.unique_for_month
Like :attr:`~Field.unique_for_date`, but requires the field to be unique with
respect to the month.
``unique_for_year``
-------------------
.. attribute:: Field.unique_for_year
Like :attr:`~Field.unique_for_date` and :attr:`~Field.unique_for_month`.
``verbose_name``
-------------------
.. attribute:: 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 :ref:`Verbose field names <verbose-field-names>`.
``validators``
-------------------
.. attribute:: Field.validators
A list of validators to run for this field. See the :doc:`validators
documentation </ref/validators>` for more information.
Registering and fetching lookups
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
``Field`` implements the :ref:`lookup registration API <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.
.. _model-field-types:
Field types
===========
.. currentmodule:: django.db.models
``AutoField``
-------------
.. class:: AutoField(**options)
An :class:`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 :ref:`automatic-primary-key-fields`.
``BigIntegerField``
-------------------
.. class:: BigIntegerField(**options)
A 64 bit integer, much like an :class:`IntegerField` except that it is
guaranteed to fit numbers from ``-9223372036854775808`` to
``9223372036854775807``. The default form widget for this field is a
:class:`~django.forms.TextInput`.
``BinaryField``
-------------------
.. class:: BinaryField(**options)
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.
.. admonition:: 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 :doc:`static files </howto/static-files/index>` handling.
``BooleanField``
----------------
.. class:: BooleanField(**options)
A true/false field.
The default form widget for this field is a
:class:`~django.forms.CheckboxInput`.
If you need to accept :attr:`~Field.null` values then use
:class:`NullBooleanField` instead.
The default value of ``BooleanField`` is ``None`` when :attr:`Field.default`
isn't defined.
``CharField``
-------------
.. class:: CharField(max_length=None, **options)
A string field, for small- to large-sized strings.
For large amounts of text, use :class:`~django.db.models.TextField`.
The default form widget for this field is a :class:`~django.forms.TextInput`.
:class:`CharField` has one extra required argument:
.. attribute:: 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.
.. note::
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 :doc:`database backend
notes </ref/databases>` for details.
.. admonition:: MySQL users
If you are using this field with MySQLdb 1.2.2 and the ``utf8_bin``
collation (which is *not* the default), there are some issues to be aware
of. Refer to the :ref:`MySQL database notes <mysql-collation>` for
details.
``CommaSeparatedIntegerField``
------------------------------
.. class:: CommaSeparatedIntegerField(max_length=None, **options)
A field of integers separated by commas. As in :class:`CharField`, the
:attr:`~CharField.max_length` argument is required and the note about database
portability mentioned there should be heeded.
``DateField``
-------------
.. class:: DateField(auto_now=False, auto_now_add=False, **options)
A date, represented in Python by a ``datetime.date`` instance. Has a few extra,
optional arguments:
.. attribute:: 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.
.. attribute:: 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 ``default=timezone.now``
(from :func:`django.utils.timezone.now`) instead of ``auto_now_add=True``.
The default form widget for this field is a
:class:`~django.forms.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.
.. note::
As currently implemented, setting ``auto_now`` or ``auto_now_add`` to
``True`` will cause the field to have ``editable=False`` and ``blank=True``
set.
.. note::
The ``auto_now`` and ``auto_now_add`` options will always use the date in
the :ref:`default timezone <default-current-time-zone>` 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``
-----------------
.. class:: DateTimeField(auto_now=False, auto_now_add=False, **options)
A date and time, represented in Python by a ``datetime.datetime`` instance.
Takes the same extra arguments as :class:`DateField`.
The default form widget for this field is a single
:class:`~django.forms.TextInput`. The admin uses two separate
:class:`~django.forms.TextInput` widgets with JavaScript shortcuts.
``DecimalField``
----------------
.. class:: DecimalField(max_digits=None, decimal_places=None, **options)
A fixed-precision decimal number, represented in Python by a
:class:`~decimal.Decimal` instance. Has two **required** arguments:
.. attribute:: 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``.
.. attribute:: 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 :class:`~django.forms.NumberInput`
when :attr:`~django.forms.Field.localize` is ``False`` or
:class:`~django.forms.TextInput` otherwise.
.. note::
For more information about the differences between the
:class:`FloatField` and :class:`DecimalField` classes, please
see :ref:`FloatField vs. DecimalField <floatfield_vs_decimalfield>`.
``DurationField``
-----------------
.. versionadded:: 1.8
.. class:: DurationField(**options)
A field for storing periods of time - modeled in Python by
:class:`~python:datetime.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.
.. note::
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``
--------------
.. class:: EmailField(max_length=254, **options)
A :class:`CharField` that checks that the value is a valid email address. It
uses :class:`~django.core.validators.EmailValidator` to validate the input.
.. versionchanged:: 1.8
The default ``max_length`` was increased from 75 to 254 in order to be
compliant with RFC3696/5321.
``FileField``
-------------
.. class:: FileField(upload_to=None, max_length=100, **options)
A file-upload field.
.. note::
The ``primary_key`` and ``unique`` arguments are not supported, and will
raise a ``TypeError`` if used.
Has two optional arguments:
.. attribute:: 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
:meth:`Storage.save() <django.core.files.storage.Storage.save>` method.
If you specify a string value, it may contain :func:`~time.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
:class:`~django.core.files.storage.FileSystemStorage`, the string value
will be appended to your :setting:`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 Description
====================== ===============================================
``instance`` An instance of the model where the
``FileField`` is defined. More specifically,
this is the particular instance where the
current file is being attached.
In most cases, this object will not have been
saved to the database yet, so if it uses the
default ``AutoField``, *it might not yet have a
value for its primary key field*.
``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.
====================== ===============================================
For example::
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)
.. attribute:: FileField.storage
A storage object, which handles the storage and retrieval of your
files. See :doc:`/topics/files` for details on how to provide this object.
The default form widget for this field is a
:class:`~django.forms.ClearableFileInput`.
Using a :class:`FileField` or an :class:`ImageField` (see below) in a model
takes a few steps:
1. In your settings file, you'll need to define :setting:`MEDIA_ROOT` as the
full path to a directory where you'd like Django to store uploaded files.
(For performance, these files are not stored in the database.) Define
:setting:`MEDIA_URL` as the base public URL of that directory. Make sure
that this directory is writable by the Web server's user account.
2. Add the :class:`FileField` or :class:`ImageField` to your model, defining
the :attr:`~FileField.upload_to` option to specify a subdirectory of
:setting:`MEDIA_ROOT` to use for uploaded files.
3. All that will be stored in your database is a path to the file
(relative to :setting:`MEDIA_ROOT`). You'll most likely want to use the
convenience :attr:`~django.db.models.fields.files.FieldFile.url` attribute
provided by Django. For example, if your :class:`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 :setting:`MEDIA_ROOT` is set to ``'/home/media'``, and
:attr:`~FileField.upload_to` is set to ``'photos/%Y/%m/%d'``. The ``'%Y/%m/%d'``
part of :attr:`~FileField.upload_to` is :func:`~time.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 :attr:`~django.core.files.File.name` and
:attr:`~django.core.files.File.size` attributes respectively; for more
information on the available attributes and methods, see the
:class:`~django.core.files.File` class reference and the :doc:`/topics/files`
topic guide.
.. note::
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
:attr:`~django.db.models.fields.files.FieldFile.url` attribute. Internally,
this calls the :meth:`~django.core.files.storage.Storage.url` method of the
underlying :class:`~django.core.files.storage.Storage` class.
.. _file-upload-security:
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.
:class:`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 :attr:`~CharField.max_length` argument.
FileField and FieldFile
~~~~~~~~~~~~~~~~~~~~~~~
.. currentmodule:: django.db.models.fields.files
.. class:: FieldFile
When you access a :class:`~django.db.models.FileField` on a model, you are
given an instance of :class:`FieldFile` as a proxy for accessing the underlying
file. In addition to the functionality inherited from
:class:`django.core.files.File`, this class has several attributes and methods
that can be used to interact with file data:
.. attribute:: FieldFile.url
A read-only property to access the file's relative URL by calling the
:meth:`~django.core.files.storage.Storage.url` method of the underlying
:class:`~django.core.files.storage.Storage` class.
.. method:: FieldFile.open(mode='rb')
Behaves like the standard Python ``open()`` method and opens the file
associated with this instance in the mode specified by ``mode``.
.. method:: FieldFile.close()
Behaves like the standard Python ``file.close()`` method and closes the file
associated with this instance.
.. method:: FieldFile.save(name, content, save=True)
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
:class:`~django.db.models.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
:class:`django.core.files.File`, not Python's built-in file object.
You can construct a :class:`~django.core.files.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('/tmp/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 :doc:`/topics/files`.
.. method:: FieldFile.delete(save=True)
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).
.. currentmodule:: django.db.models
``FilePathField``
-----------------
.. class:: FilePathField(path=None, match=None, recursive=False, max_length=100, **options)
A :class:`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**:
.. attribute:: FilePathField.path
Required. The absolute filesystem path to a directory from which this
:class:`FilePathField` should get its choices. Example: ``"/home/images"``.
.. attribute:: FilePathField.match
Optional. A regular expression, as a string, that :class:`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``.
.. attribute:: FilePathField.recursive
Optional. Either ``True`` or ``False``. Default is ``False``. Specifies
whether all subdirectories of :attr:`~FilePathField.path` should be included
.. attribute:: FilePathField.allow_files
Optional. Either ``True`` or ``False``. Default is ``True``. Specifies
whether files in the specified location should be included. Either this or
:attr:`~FilePathField.allow_folders` must be ``True``.
.. attribute:: FilePathField.allow_folders
Optional. Either ``True`` or ``False``. Default is ``False``. Specifies
whether folders in the specified location should be included. Either this
or :attr:`~FilePathField.allow_files` must be ``True``.
Of course, these arguments can be used together.
The one potential gotcha is that :attr:`~FilePathField.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 :attr:`~FilePathField.match` applies to the base filename
(``foo.png`` and ``bar.png``).
:class:`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 :attr:`~CharField.max_length` argument.
``FloatField``
--------------
.. class:: FloatField(**options)
A floating-point number represented in Python by a ``float`` instance.
The default form widget for this field is a :class:`~django.forms.NumberInput`
when :attr:`~django.forms.Field.localize` is ``False`` or
:class:`~django.forms.TextInput` otherwise.
.. _floatfield_vs_decimalfield:
.. admonition:: ``FloatField`` vs. ``DecimalField``
The :class:`FloatField` class is sometimes mixed up with the
:class:`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 :mod:`decimal` module.
``ImageField``
--------------
.. class:: ImageField(upload_to=None, height_field=None, width_field=None, max_length=100, **options)
Inherits all attributes and methods from :class:`FileField`, but also
validates that the uploaded object is a valid image.
In addition to the special attributes that are available for :class:`FileField`,
an :class:`ImageField` also has ``height`` and ``width`` attributes.
To facilitate querying on those attributes, :class:`ImageField` has two extra
optional arguments:
.. attribute:: 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.
.. attribute:: 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.
.. _Pillow: http://pillow.readthedocs.org/en/latest/
:class:`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 :attr:`~CharField.max_length` argument.
The default form widget for this field is a
:class:`~django.forms.ClearableFileInput`.
``IntegerField``
----------------
.. class:: IntegerField(**options)
An integer. Values from ``-2147483648`` to ``2147483647`` are safe in all
databases supported by Django. The default form widget for this field is a
:class:`~django.forms.NumberInput` when :attr:`~django.forms.Field.localize`
is ``False`` or :class:`~django.forms.TextInput` otherwise.
``GenericIPAddressField``
-------------------------
.. class:: GenericIPAddressField(protocol=both, unpack_ipv4=False, **options)
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
:class:`~django.forms.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.
.. attribute:: GenericIPAddressField.protocol
Limits valid inputs to the specified protocol.
Accepted values are ``'both'`` (default), ``'IPv4'``
or ``'IPv6'``. Matching is case insensitive.
.. attribute:: 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``
--------------------
.. class:: NullBooleanField(**options)
Like a :class:`BooleanField`, but allows ``NULL`` as one of the options. Use
this instead of a :class:`BooleanField` with ``null=True``. The default form
widget for this field is a :class:`~django.forms.NullBooleanSelect`.
``PositiveIntegerField``
------------------------
.. class:: PositiveIntegerField(**options)
Like an :class:`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``
-----------------------------
.. class:: PositiveSmallIntegerField(**options)
Like a :class:`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``
-------------