Field options¶
The following arguments are available to all field types. All are optional.
null¶
-
Field.null¶
If True, Django will store empty values as NULL in the database. Default
is False.
Note that empty string values will always get stored as empty strings, not as
NULL. Only use null=True for non-string fields such as integers,
booleans and dates. For both types of 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).
Avoid using null on string-based fields such as
CharField and TextField unless you have an excellent reason.
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;” Django convention is to use the empty
string, not NULL.
Note
When using the Oracle database backend, the null=True option will be
coerced for string-based fields that have the empty string as a possible
value, and the value NULL will be stored to denote the empty string.
blank¶
-
Field.blank¶
If True, the field is allowed to be blank. Default is False.
Note that this is different than null. null is
purely database-related, whereas blank is validation-related. If
a field has blank=True, validation on Django’s admin site 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) of 2-tuples to use as choices for this
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 this:
YEAR_IN_SCHOOL_CHOICES = (
('FR', 'Freshman'),
('SO', 'Sophomore'),
('JR', 'Junior'),
('SR', 'Senior'),
('GR', 'Graduate'),
)
The first element in each tuple is the actual value to be stored. The second
element is the human-readable name for the option.
The choices list can be defined either as part of your model class:
class Foo(models.Model):
GENDER_CHOICES = (
('M', 'Male'),
('F', 'Female'),
)
gender = models.CharField(max_length=1, choices=GENDER_CHOICES)
or outside your model class altogether:
GENDER_CHOICES = (
('M', 'Male'),
('F', 'Female'),
)
class Foo(models.Model):
gender = models.CharField(max_length=1, choices=GENDER_CHOICES)
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.
Finally, 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.
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_index¶
-
Field.db_index¶
If True, djadmin:django-admin.py sqlindexes <sqlindexes> will output a
CREATE INDEX statement for this field.
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, this option is ignored.
default¶
-
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.
editable¶
-
Field.editable¶
If False, the field will not be editable in the admin or via forms
automatically generated from the model class. Default is True.
help_text¶
-
Field.help_text¶
Extra "help" text to be displayed under the field on the object's admin form.
It's useful for documentation even if your object doesn't have an admin form.
Note that this value is not HTML-escaped when it's displayed in the admin
interface. 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.
primary_key¶
-
Field.primary_key¶
If True, this field is the primary key for the model.
If you don't specify primary_key=True for any fields in your model, Django
will automatically add an IntegerField 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
Automatic primary key fields.
primary_key=True implies null=False and unique=True.
Only one primary key is allowed on an object.
unique¶
-
Field.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. 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
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.
This is enforced at the Django admin-form level but not at the database level.
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.
Field types¶
AutoField¶
-
class AutoField(**options)¶
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 Automatic primary key fields.
BooleanField¶
-
class BooleanField(**options)¶
A true/false field.
The admin represents this as a checkbox.
MySQL users..
A boolean field in MySQL is stored as a TINYINT column with a value of
either 0 or 1 (most databases have a proper BOOLEAN type instead). So,
for MySQL, only, when a BooleanField is retrieved from the database
and stored on a model attribute, it will have the values 1 or 0, rather
than True or False. Normally, this shouldn't be a problem, since
Python guarantees that 1 == True and 0 == False are both true.
Just be careful if you're writing something like obj is True when
obj is a value from a boolean attribute on a model. If that model was
constructed using the mysql backend, the "is" test will fail.
Prefer an equality test (using "==") in cases like this.
CharField¶
-
class CharField(max_length=None[, **options])¶
A string field, for small- to large-sized strings.
For large amounts of text, use TextField.
The admin represents this as an <input type="text"> (a single-line input).
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.
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 database backend
notes for details.
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 MySQL database notes for
details.
CommaSeparatedIntegerField¶
-
class CommaSeparatedIntegerField(max_length=None[, **options])¶
A field of integers separated by commas. As in CharField, the
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:
-
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.
-
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.
The admin represents this as an <input type="text"> with a JavaScript
calendar, and a shortcut for "Today". The JavaScript calendar will always
start the week on a Sunday.
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 DateField.
The admin represents this as two <input type="text"> fields, with
JavaScript shortcuts.
DecimalField¶
-
class DecimalField(max_digits=None, decimal_places=None[, **options])¶
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
-
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 admin represents this as an <input type="text"> (a single-line input).
EmailField¶
-
class EmailField([max_length=75, **options])¶
A CharField that checks that the value is a valid e-mail address.
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 one required argument:
-
FileField.upload_to¶
-
A local filesystem path that will be appended to your MEDIA_ROOT
setting to determine the value of the url
attribute.
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).
This may also be a callable, such as a function, which will be called to
obtain the upload path, including the filename. This callable must be able
to accept two arguments, and return a Unix-style path (with forward slashes)
to be passed along to the storage system. The two arguments that will be
passed 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. |
Also has one optional argument:
-
FileField.storage¶
-
Optional. A storage object, which handles the storage and retrieval of your
files. See Managing files for details on how to provide this object.
The admin represents this field as an <input type="file"> (a file-upload
widget).
Using a FileField or an ImageField (see below) in a model
takes a few steps:
- In your settings file, you'll need to define 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
MEDIA_URL as the base public URL of that directory. Make sure
that this directory is writable by the Web server's user account.
- Add the FileField or ImageField to your model, making
sure to define the upload_to option to tell Django
to which subdirectory of MEDIA_ROOT it should upload files.
- All that will be stored in your database is a path to the file
(relative to MEDIA_ROOT). You'll most likely want to use the
convenience url function provided by
Django. For example, if your ImageField is called mug_shot,
you can get the absolute URL 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 want to retrieve the upload file's on-disk filename, or a URL that refers
to that file, or the file's size, you can use the
name, url
and size attributes; see Managing files.
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.
New in Django 1.0: The max_length argument was added in this version.
By default, FileField instances are
created as varchar(100) columns in your database. As with other fields, you
can change the maximum length using the max_length argument.
FilePathField¶
-
class FilePathField(path=None[, match=None, recursive=False, max_length=100, **options])¶
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.gif.
-
FilePathField.recursive¶
- Optional. Either True or False. Default is False. Specifies
whether all subdirectories of path should be included
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.gif but not /home/images/foo/bar.gif
because the match applies to the base filename
(foo.gif and bar.gif).
New in Django 1.0: The max_length argument was added in this version.
By default, FilePathField instances are
created as varchar(100) columns in your database. As with other fields, you
can change the maximum length using the max_length argument.
FloatField¶
-
class FloatField([**options])¶
A floating-point number represented in Python by a float instance.
The admin represents this as an <input type="text"> (a single-line input).
ImageField¶
-
class ImageField(upload_to=None[, height_field=None, width_field=None, max_length=100, **options])¶
Like FileField, but validates that the uploaded object is a valid
image. 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.
In addition to the special attributes that are available for FileField,
an ImageField also has File.height and File.width attributes.
See Managing files.
Requires the Python Imaging Library.
New in Django 1.0: The max_length argument was added in this version.
By default, ImageField instances are
created as varchar(100) columns in your database. As with other fields, you
can change the maximum length using the max_length argument.
IntegerField¶
-
class IntegerField([**options])¶
An integer. The admin represents this as an <input type="text"> (a
single-line input).
IPAddressField¶
-
class IPAddressField([**options])¶
An IP address, in string format (e.g. "192.0.2.30"). The admin represents this
as an <input type="text"> (a single-line input).
NullBooleanField¶
-
class NullBooleanField([**options])¶
Like a BooleanField, but allows NULL as one of the options. Use
this instead of a BooleanField with null=True. The admin represents
this as a <select> box with "Unknown", "Yes" and "No" choices.
PositiveIntegerField¶
-
class PositiveIntegerField([**options])¶
Like an IntegerField, but must be positive.
PositiveSmallIntegerField¶
-
class PositiveSmallIntegerField([**options])¶
Like a PositiveIntegerField, but only allows values under a certain
(database-dependent) point.
SlugField¶
-
class SlugField([max_length=50, **options])¶
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.
SmallIntegerField¶
-
class SmallIntegerField([**options])¶
Like an IntegerField, but only allows values under a certain
(database-dependent) point.
TextField¶
-
class TextField([**options])¶
A large text field. The admin represents this as a <textarea> (a multi-line
input).
MySQL users
If you are using this field with MySQLdb 1.2.1p2 and the utf8_bin
collation (which is not the default), there are some issues to be aware
of. Refer to the MySQL database notes for
details.
TimeField¶
-
class TimeField([auto_now=False, auto_now_add=False, **options])¶
A time, represented in Python by a datetime.time instance. Accepts the same
auto-population options as DateField.
The admin represents this as an <input type="text"> with some JavaScript
shortcuts.
URLField¶
-
class URLField([verify_exists=True, max_length=200, **options])¶
A CharField for a URL. Has one extra optional argument:
-
URLField.verify_exists¶
- If True (the default), the URL given will be checked for existence
(i.e., the URL actually loads and doesn't give a 404 response). It should
be noted that when using the single-threaded development server, validating
a url being serverd by the same server will hang.
This should not be a problem for multithreaded servers.
The admin represents this as an <input type="text"> (a single-line input).
Like all CharField subclasses, URLField takes the optional
max_length, a default of 200 is used.
XMLField¶
-
class XMLField(schema_path=None[, **options])¶
A TextField that checks that the value is valid XML that matches a
given schema. Takes one required argument:
-
schema_path¶
- The filesystem path to a RelaxNG schema against which to validate the
field.