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.

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.

unique_for_year¶

Field.unique_for_year¶

Like unique_for_date and unique_for_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.

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.

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.

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.

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).

Changed in Django 1.0: Please, see the release notes

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¶

New in Django 1.0: Please, see the release notes

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:

1. 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.
2. 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.
3. 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.

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).

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.

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).

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.

ForeignKey¶

class ForeignKey(othermodel[, **options])¶

A many-to-one relationship. Requires a positional argument: the class to which the model is related.

To create a recursive relationship -- an object that has a many-to-one relationship with itself -- use models.ForeignKey('self').

If you need to create a relationship on a model that has not yet been defined, you can use the name of the model, rather than the model object itself:

class Car(models.Model):
    manufacturer = models.ForeignKey('Manufacturer')
    # ...

class Manufacturer(models.Model):
    # ...

To refer to models defined in another application, you can explicitly specify a model with the full application label. For example, if the Manufacturer model above is defined in another application called production, you'd need to use:

class Car(models.Model):
    manufacturer = models.ForeignKey('production.Manufacturer')

This sort of reference can be useful when resolving circular import dependencies between two applications.

ManyToManyField¶

class ManyToManyField(othermodel[, **options])¶

A many-to-many relationship. Requires a positional argument: the class to which the model is related. This works exactly the same as it does for ForeignKey, including all the options regarding recursive and lazy relationships.

OneToOneField¶

class OneToOneField(othermodel[, parent_link=False, **options])¶

A one-to-one relationship. Conceptually, this is similar to a ForeignKey with unique=True, but the "reverse" side of the relation will directly return a single object.

This is most useful as the primary key of a model which "extends" another model in some way; Multi-table inheritance is implemented by adding an implicit one-to-one relation from the child model to the parent model, for example.

One positional argument is required: the class to which the model will be related. This works exactly the same as it does for ForeignKey, including all the options regarding recursive and lazy relationships.

Additionally, OneToOneField accepts all of the extra arguments accepted by ForeignKey, plus one extra argument:

OneToOneField.parent_link¶

When True and used in a model which inherits from another (concrete) model, indicates that this field should be used as the link back to the parent class, rather than the extra OneToOneField which would normally be implicitly created by subclassing.