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Copy-edited model-API docs 

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@ -3,14 +3,14 @@ Model reference
===============
Django's models are the bread and butter of the framework. There's a huge
array of options available to you when defining your data models; this
document explains all of them.
array of options available to you when defining your data models. This
document explains them.
Options for models
==================
A list of all possible options for a model object follows. Although there's a
wide array of possible options, only ``fields`` is required.
wide array of options, only ``fields`` is required.
``admin``
A ``meta.Admin`` object; see `Admin options`_. If this field isn't given,
@ -21,7 +21,7 @@ wide array of possible options, only ``fields`` is required.
db_table = "pizza_orders"
If not given, this will use ``app_label + '_' + module_name``.
If this isn't given, Django will use ``app_label + '_' + module_name``.
``exceptions``
Names of extra exception subclasses to include in the generated module.
@ -31,7 +31,7 @@ wide array of possible options, only ``fields`` is required.
exceptions = ("DisgustingToppingsException", "BurntCrust")
``fields``
A list of field objects; see `Field objects`_. For example::
A list of field objects. See `Field objects`_. For example::
fields = (
meta.CharField('customer_name', 'customer name', maxlength=15),
@ -41,14 +41,14 @@ wide array of possible options, only ``fields`` is required.
)
``get_latest_by``
The name of a date or datetime field; if given, the module will have a
``get_latest()`` function which fetches the "latest" object in terms of
that field::
The name of a ``DateField`` or ``DateTimeField``; if given, the module will
have a ``get_latest()`` function that fetches the "latest" object according
to that field::
get_latest_by = "order_date"
``module_constants``
A dict of name/values to use as extra module-level constants::
A dictionary of names/values to use as extra module-level constants::
module_constants = {
'MEAT_TYPE_PEPPERONI' : 1,
@ -60,7 +60,8 @@ wide array of possible options, only ``fields`` is required.
module_name = "pizza_orders"
If not given this will use a lowercased version of the class name.
If this isn't given, Django will use a lowercased version of the class
name, plus "s".
``order_with_respect_to``
Marks this object as "orderable" with respect to the given field. This is
@ -73,20 +74,20 @@ wide array of possible options, only ``fields`` is required.
to allow the toppings to be ordered with respect to the associated pizza.
``ordering``
The default ordering for tho object::
The default ordering for the object, for use by ``get_list`` and the admin::
ordering = (('order_date', 'DESC'),)
This is a tuple of 2-tuples; each 2-tuple is ``(field_name, ordering_type)``
where ordering_type is either ``"ASC"`` or ``"DESC"``. You may also use the
magic ``(None, "RANDOM")`` ordering tuple for random ordering.
This is a tuple of 2-tuples. Each 2-tuple is ``(field_name, ordering_type)``
where ordering_type is either ``"ASC"`` or ``"DESC"``. You can also use the
``(None, "RANDOM")`` for random ordering.
``permissions``
Extra permissions to enter into the permissions table when creating this
object. A add, delete, and change permission is automatically created for
each object; this option specifies extra permissions::
each object. This option specifies extra permissions::
permissions = (("may_delivier_pizzas", "Can deliver pizzas"),)
permissions = (("can_delivier_pizzas", "Can deliver pizzas"),)
This is a list of 2-tuples of
``(permission_code, human_readable_permission_name)``.
@ -97,14 +98,14 @@ wide array of possible options, only ``fields`` is required.
unique_together = (("driver_id", "restaurant_id"),)
This is a list of lists of fields that must be unique when considered
together.
together. It's used in the Django admin.
``verbose_name``
A human-readable name for the object, singular::
verbose_name = "pizza"
If not given, this will use a munged version of the class name:
If this isn't given, Django will use a munged version of the class name:
``CamelCase`` becomes ``camel case``.
``verbose_name_plural``
@ -112,13 +113,13 @@ wide array of possible options, only ``fields`` is required.
verbose_name_plural = "stories"
If not given, ``verbose_name + "s"`` will automatically be used.
If this isn't given, Django will use ``verbose_name + "s"``.
Field objects
=============
The list of fields is the most important part of a data model. Each item in
the ``fields`` list is an instance of a ``meta.Field`` subclass, and maps to
the ``fields`` list is an instance of a ``meta.Field`` subclass and maps to
a database field.
All field objects -- except for ``ForeignKey`` and ``ManyToManyField`` (see
@ -130,8 +131,8 @@ contain spaces, punctuation, etc.
General field options
---------------------
Each type of field takes a different set of options, but there are some
options that are common to all field types. These options are:
Each type of field takes a different set of options, but some options are
common to all field types. These options are:
====================== ===================================================
Option Description
@ -139,14 +140,15 @@ options that are common to all field types. These options are:
``blank`` If ``True``, the field is allowed to be blank.
Note that this is different from ``null`` in that
string fields will store the empty string instead of
``NULL`` internally; this means that to create a
``NULL`` internally. This means that to create a
field that stores nulls you must pass ``blank=True``
and ``null=True`` .
and ``null=True``.
``choices`` A list of 2-tuples to use as choices for this
field.If this is given, instead of the standard
field a option menu will be used, limiting choices
to the choices given. A choices list looks like::
field. If this is given, Django's admin will use a
select box instead of the standard text field and
will limit choices to the choices given. A choices
list looks like::
YEAR_IN_SCHOOL_CHOICES = (
('FR', 'Freshman'),
@ -157,8 +159,8 @@ options that are common to all field types. These options are:
)
The first element in each tuple is the actual value
to be stored; the second element is the human
readable name for the option.
to be stored. The second element is the
human-readable name for the option.
``core`` For objects that are edited inline to a related
object. If all "core" fields in an inline-edited
@ -173,35 +175,37 @@ options that are common to all field types. These options are:
``default`` The default value for the field.
``editable`` ``True`` by default, if set to ``False`` the field
will not be editable in the admin.
``editable`` ``True`` by default. If this is set to ``False``,
the field will not be editable in the admin.
``help_text`` Extra "help" text to be displayed with the field.
``help_text`` Extra "help" text to be displayed under the field
on the object's admin form.
``null`` If ``True`` empty values in the field will be
``null`` If ``True``, empty values in the field will be
stored as ``NULL`` in the database.
``primary_key`` If ``True`` this field is the primary key for the
``primary_key`` If ``True``, this field is the primary key for the
table. You only need to use this if you don't want
the standard "id" field created and used as the
primary key.
Implies ``blank=False``, ``null=False``, and
``unique=True``. Only one primary key is allowed
on each object.
on an object.
``radio_admin`` If ``choices`` is given, or if the field is a
ManyToOne relation, use a radio button interface
for the choices instead of the standard options
menu interface.
ManyToOne relation, use a radio-button interface
for the choices instead of the standard select-box
interface.
``unique`` If ``True`` this field must be unique throughout
the table.
``unique`` If ``True``, this field must be unique throughout
the table. This is enforced at the database level
and at the Django admin-form level.
``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. That
is, if you have a field, ``title`` that has
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 it is an
error to have two rows with the same ``title``
and the same ``pub_date``.
@ -209,23 +213,18 @@ options that are common to all field types. These options are:
``unique_for_month`` Like ``unique_for_date``, but requires the field
to be unique with respect to the month.
``unique_for_year`` Like ``unique_for_date`` and ``unique_for_month``
but, well, you get the idea.
``unique_for_year`` Like ``unique_for_date`` and ``unique_for_month``.
``validator_list`` A list of extra validators to apply to the field.
See the `Form fields guide`_ for information about
validators.
====================== ===================================================
.. _`Form fields guide`: http://www.djangoproject.com/FIXME/
Field Types
-----------
``AutoField``
An ``IntegerField`` that automatically increments. 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. That automatically added field is::
model if you don't specify otherwise. That automatically-added field is::
meta.AutoField('id', 'ID', primary_key=True)
@ -234,16 +233,17 @@ Field Types
``CharField``
A text field. These are displayed in the admin as single-line text inputs, so
for large amounts of text use a ``TextField``.
for large amounts of text, use a ``TextField``.
``CharField``s have an extra required argument: ``maxlength``; the maximum
length (in characters) of the field.
``CharField``s have an extra required argument: ``maxlength``, the maximum
length (in characters) of the field. The maxlength is enforced at the database
level and in Django's admin validation.
``CommaSeparatedIntegerField``
A field of integers separated by commas.
``DateField``
A, um, date field. Has a few extra optional options:
A date field. Has a few extra optional options:
====================== ===================================================
Option Description
@ -253,22 +253,23 @@ Field Types
timestamps.
``auto_now_add`` Automatically set the field to now when the object
is first created. Useful for creation timestamps.
is first created. Useful for creation of
timestamps.
====================== ===================================================
``DateTimeField``
A date and time field. Takes the same extra options as ``DateField``.
``EmailField``
A ``CharField`` that checks that the value is a valid email address. Because
validating email addresses can be tricky, this is a pretty loose test.
A ``CharField`` that checks that the value is a valid e-mail address.
Because validating e-mail addresses can be tricky, this is a pretty loose
test.
``FileField``
A file-upload field. Takes on additional option, ``upload_to`` which is
a path to upload the file to. This path 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).
A file-upload field. Takes an additional option, ``upload_to``, which is
a local filesystem path to upload the file to. This path 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).
.. _`strftime formatting`: http://docs.python.org/lib/module-time.html#l2h-1941
@ -312,16 +313,16 @@ Field Types
interface.
``edit_inline_type`` This is either ``meta.TABULAR`` or
``meta.STACKED`` and controls weather the inline
``meta.STACKED`` and controls whether the inline
editable objects are displayed as a table or as
a "stack" of fieldsets. Defaults to
``meta.STACKED``.
``limit_choices_to`` A dictionary of lookup arguments and values (see
the `Database API reference`_) to limit choices
of this object to. Use this along with
``meta.LazyDate`` to limit choices of objects
by date, for example::
the `Database API reference`_) that limit the
available admin choices for this object. Use this
with ``meta.LazyDate`` to limit choices of objects
by date. For example::
limit_choices_to = {'pub_date__lte' : meta.LazyDate()}
@ -338,18 +339,19 @@ Field Types
that a user never enters more than 10 toppings.
Note that this doesn't ensure more than 10 related
toppings ever get created.
toppings ever get created. It just controls the
interface.
``min_num_in_admin`` The minimum number of related objects displayed in
the admin. Normally, at the creation stage
the admin. Normally, at the creation stage,
``num_in_admin`` inline objects are shown, and at
the edit stage ``num_extra_on_change`` objects are
shown in addition to all pre-existing related
objects. However, no fewer than
the edit stage ``num_extra_on_change`` blank
objects are shown in addition to all pre-existing
related objects. However, no fewer than
``min_num_in_admin`` related objects will ever be
displayed.
``num_extra_on_change`` The number of extra blank related object fields to
``num_extra_on_change`` The number of extra blank related-object fields to
show at the change stage.
``num_in_admin`` The default number of inline objects to display
@ -358,14 +360,14 @@ Field Types
``raw_id_admin`` Only display a field for the integer to be entered
instead of a drop-down menu. This is useful when
related to an object type that will have too many
rows to make a menu practical.
rows to make a select box practical.
Not used with ``edit_inline``.
``rel_name`` The name of the relation. In the above example,
this would default to 'pizza' (so that the
``Toppings`` object would have a ``get_pizza()``
function; if you set ``rel_name`` to "pie", then
function. If you set ``rel_name`` to "pie", then
the function would be called ``get_pie()`` and the
field name would be ``pie_id``.
@ -411,7 +413,7 @@ Field Types
``to_field`` The field on the related object that the relation
is to. This is almost always ``id``, but if the
PK on the other object is named something
primary key on the other object is named something
different, this is how to indicate that.
======================= ============================================================
@ -422,8 +424,12 @@ Field Types
image. Has two extra optional arguments, ``height_field`` and ``width_field``
which, if set, will be auto-populated with the height and width of the image.
Requires the `Python Imaging Library`_.
.. _Python Imaging Library: http://www.pythonware.com/products/pil/
``IntegerField``
An integer, surprisingly.
An integer.
``IPAddressField``
An IP address, in string format (i.e. "24.124.1.30").
@ -439,9 +445,9 @@ Field Types
)
Many-to-many relations are a bit different from other fields. First, they
aren't actually a field per se since they use a intermediary join table.
Second, they don't take any of the same options as the rest of the fields,
the only options taken are:
aren't actually a field per se, because they use a intermediary join table.
Second, they don't take any of the same options as the rest of the fields.
The only options taken are:
======================= ============================================================
Option Description
@ -450,9 +456,10 @@ Field Types
``ManyToOneField``, above.
``filter_interface`` Use a nifty unobtrusive Javascript "filter" interface
instead of the usability-challenged ``<select multiple>``.
The value should be ``meta.HORIZONTAL`` or ``meta.VERTICAL``
(i.e. should the interface be stacked horizontally or
instead of the usability-challenged ``<select multiple>``
in the admin form for this object. The value should be
``meta.HORIZONTAL`` or ``meta.VERTICAL`` (i.e.
should the interface be stacked horizontally or
vertically).
``limit_choices_to`` See the description under ``ManyToOneField``, above.
@ -460,7 +467,7 @@ Field Types
``NullBooleanField``
Like a ``BooleanField``, but allows ``NULL`` as one of the options. Use this
instead of a ``BooleanField`` with ``null=True`` .
instead of a ``BooleanField`` with ``null=True``.
``OneToOneField``
Signifies a one-to-one relationship. This is most useful on the primary key
@ -490,19 +497,22 @@ Field Types
Like an ``IntegerField``, but must be positive.
``PositiveSmallIntegerField``
Like a ``PositiveIntegerField``, but only allows values below 32767.
Like a ``PositiveIntegerField``, but only allows values under a certain
(database-dependent) point.
``SlugField``
A "slug" suitable for parts of a URL; only allows alpha-numeric characters and
underscores.
A "slug," suitable for parts of a URL. Only allows alphanumeric characters
and underscores.
Implies ``maxlength=50`` and ``db_index=True``.
Accepts an extra option, ``prepopulate_from`` which is a list of fields from
which to auto-populate the slug.
Accepts an extra option, ``prepopulate_from``, which is a list of fields
from which to auto-populate the slug, via JavaScript, in the object's admin
form.
``SmallIntegerField``
Like an ``IntegerField``, but must be between -32768 and 32767.
Like an ``IntegerField``, but only allows values under a certain
(database-dependent) point.
``TextField``
A large text field (``<textarea>`` in HTML).
@ -512,16 +522,17 @@ Field Types
``DateTimeField``.
``URLField``
A field for a URL. If the ``verify_exists`` option is ``True``, the URL given
will be checked for existence (i.e. actually loads and doesn't give a 404
response).
A field for a URL. If the ``verify_exists`` option is ``True`` (default),
the URL given will be checked for existence (i.e., the URL actually loads
and doesn't give a 404 response).
``USStateField``
A US state.
A two-letter U.S. state abbreviation.
``XMLField``
A field containing XML. Takes one required argument, ``schema_path`` which
is the path to a RelaxNG_ scheme against which to validate the field.
A field containing XML. Takes one required argument, ``schema_path``, which
is the filesystem path to a RelaxNG_ schema against which to validate the
field.
.. _RelaxNG: http://www.relaxng.org/
@ -553,14 +564,14 @@ object, which has the following options (of which only ``fields`` is required):
``classes``
Extra CSS classes to apply to the fieldset. This is a simple
string; you can apply multiple classes by separating them with
string. You can apply multiple classes by separating them with
spaces.
Two useful classes defined by the default stylesheet are ``collapse``
and ``wide``. Fieldsets with the ``collapse`` style will be
initially collapsed in the admin and replaced with a small "click
to expand" link. Fieldsets with the ``wide`` style will be given
extra horizontal space.
Two useful classes defined by the default stylesheet are
``collapse`` and ``wide``. Fieldsets with the ``collapse`` style
will be initially collapsed in the admin and replaced with a small
"click to expand" link. Fieldsets with the ``wide`` style will be
given extra horizontal space.
For example (taken from the ``core.flatfiles`` model)::
@ -579,9 +590,9 @@ object, which has the following options (of which only ``fields`` is required):
.. image:: http://media.djangoproject.com/img/doc/flatfiles_admin.png
``js``
Extra JavaScript files to link into the admin screen. This can be used to
tweak a given type of admin page in JS or to provide "quick links" to fill
in default values for certain fields.
A list of strings representing URLs of JavaScript files to link into the
admin screen. This can be used to tweak a given type of admin page in JS or
to provide "quick links" to fill in default values for certain fields.
``list_display``
List of fields to display on the list page in the admin.
@ -595,24 +606,24 @@ object, which has the following options (of which only ``fields`` is required):
* If the field is a ``BooleanField``, a "on" or "off" icon will
be displayed instead of ``True`` or ``False``.
* If the field name given does not exist, a function of the model
will be searched for and called if present. This function
should have a ``short_description`` attribute that will be
used as the header for the field.
* If the field name is a method of the model, it'll be called, and the
output will be displayed. This method should have a
``short_description`` function attribute, for use as the header for
the field.
See the exmaple below.
See the example below.
``list_filter``
List of fields to filter by. Each field should either be a ``BooleanField``
or else a field with a ``ManyToOne`` relation.
An example of how ``list_display`` and ``list_filter`` work (taken from
the ``auth.user`` model)::
Here's an example of how ``list_display`` and ``list_filter`` work (taken
from the ``auth.user`` model)::
list_display = ('username', 'email', 'first_name', 'last_name', 'is_staff'),
list_filter = ('is_staff', 'is_superuser'),
results in a admin that looks like:
This results in a admin that looks like:
.. image:: http://media.djangoproject.com/img/doc/users_changelist.png
@ -620,8 +631,8 @@ object, which has the following options (of which only ``fields`` is required):
``ordering``
An ordering tuple (see the `Options for models`_, above) that gives a
different ordering for the admin change list. If not given, the model's
default ordering will be used.
different ordering for the admin change list. If this isn't given, the
model's default ordering will be used.
``save_as``
Enables a "save as" feature on object pages. Normally, objects have three
@ -629,13 +640,17 @@ object, which has the following options (of which only ``fields`` is required):
another". If ``save_as`` is ``True``, "Save and add another" will be
replaced by a "Save as" button.
"Save as" means the object will be saved as a new object (with a new ID),
rather than the old object.
``save_on_top``
If this option is ``True``, object pages will have the save buttons across
the top as well as at the bottom of the page.
``search_fields``
A list of fields to provide a text search for. These fields should,
obviously, be some kind of text field.
A list of field names to provide a text search for. These fields should,
obviously, be some kind of text field, such as ``CharField`` or
``TextField``.
Model methods
=============
@ -650,15 +665,15 @@ of object instances. For example::
)
def is_disgusting(self):
return "anchovices" in [topping.name for topping in self.get_topping_list()]
return "anchovies" in [topping.name for topping in self.get_topping_list()]
Now, every ``Pizza`` object will have a ``is_disgusting()`` method.
There are a few object methods that have special meaning:
``__repr__``
Django uses ``repr(obj)`` in a number of places, the most notable as the
value inserted into a template when it displays an object. Thus, you should
Django uses ``repr(obj)`` in a number of places, most notably as the value
inserted into a template when it displays an object. Thus, you should
return a nice, human-readable string for the object's ``__repr__``.
``get_absolute_url``
@ -668,25 +683,26 @@ There are a few object methods that have special meaning:
def get_absolute_url(self):
return "/pizzas/%i/" % self.id
The most useful place this is used is in the admin interface; if an object
defines ``get_absolute_url`` then the object detail page will have a "View
on site" link that will jump you directly to the object's public view.
The most useful place this is used is in the admin interface. If an object
defines ``get_absolute_url``, the object detail page will have a "View on
site" link that will jump you directly to the object's public view.
``_pre_save``
This method will be called just before the object is saved into the
database; you can use it to (for example) calculate aggregate values from
other fields before the object is saved.
This method is called just before an object is saved to the database. For
example, you can use it to calculate aggregate values from other fields
before the object is saved.
``_post_save``
Called just after the object is saved to the database. This could be used
to update other tables, update cached information, etc.
This method is called just after the object is saved to the database. This
could be used to update other tables, update cached information, etc.
Module-level methods
--------------------
Since each data class in effect turns into a module, there are times you'll want
to write methods that live in that module. Any model method that begins with
"_module_" is turned into a module-level method::
Since each data class effectively turns into a "magic" Python module under
``django.models``, there are times you'll want to write methods that live in
that module. Any model method that begins with "_module_" is turned into a
module-level function::
class Pizza(meta.Model):
fields = (
@ -703,8 +719,8 @@ method::
>>> pizzas.get_pizzas_to_deliver()
[ ... ]
Note that the scope of these methods is modified to be the same has the module
scope (so that's how the raw ``get_list`` works).
Note that the scope of these methods is modified to be the same as the module
scope.
Manipulator methods
-------------------
@ -712,7 +728,7 @@ Manipulator methods
Similarly, you can add methods to the object's manipulators (see the formfields
documentation for more on manipulators) by defining methods that being with
"_manipulator_". This is most useful for providing custom validators for certain
fields since manipulators automatically call any method that begins with
fields because manipulators automatically call any method that begins with
"validate"::
class Pizza(meta.Model):
@ -726,6 +742,3 @@ fields since manipulators automatically call any method that begins with
if int(field_data) in BAD_CUSTOMER_IDS:
raise validators.ValidationError("We don't deliver to this customer")