Class Field

django.db.models.fields.Field

Base class for all field types

Declaration

@total_ordering
class Field(RegisterLookupMixin)

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Documentation

Methods

▷ def __copy__(self)
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▷ def __deepcopy__(self, memodict)
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▷ def __eq__(self, other)
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▷ def __hash__(self)
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▶ def __init__(self, verbose_name=None, name=None, primary_key=False, max_length=None, ...)
def __init__(
self,
verbose_name=None,
name=None,
primary_key=False,
max_length=None,
unique=False,
blank=False,
null=False,
db_index=False,
rel=None,
default=NOT_PROVIDED,
editable=True,
serialize=True,
unique_for_date=None,
unique_for_month=None,
unique_for_year=None,
choices=None,
help_text='',
db_column=None,
db_tablespace=None,
auto_created=False,
validators=(),
error_messages=None,
)
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Overrides
This method is overriden in:
▷ def __lt__(self, other)
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▷ def __reduce__(self)
Pickling should return the model._meta.fields instance of the field, not a new copy of that field. So, use the app registry to load the model and then the field back.
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▷ def __repr__(self)
Display the module, class, and name of the field.
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▷ def __str__(self)
Return "app_label.model_label.field_name" for fields attached to models.
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▷ def cached_col(self) @cached_property
@cached_property
def cached_col(self)
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▶ def cast_db_type(self, connection)
Return the data type to use in the Cast() function.
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Overrides
This method is overriden in:
- django.db.models.fields.CharField
▶ def check(self, **kwargs)
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Overrides
This method is overriden in:
▷ def clean(self, value, model_instance)
Convert the value's type and run validation. Validation errors from to_python() and validate() are propagated. Return the correct value if no error is raised.
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▷ def clone(self)
Uses deconstruct() to clone a new copy of this Field. Will not preserve any class attachments/attribute names.
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▶ def contribute_to_class(self, cls, name, private_only=False)
Register the field with the model class it belongs to.
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```
If private_only is True, create a separate instance of this field
for every subclass of cls, even if cls is not an abstract model.
```
Overrides
This method is overriden in:
▶ def db_check(self, connection)
Return the database column check constraint for this field, for the provided connection. Works the same way as db_type() for the case that get_internal_type() does not map to a preexisting model field.
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
- django.db.models.fields.related.ManyToManyField
▶ def db_parameters(self, connection)
Extension of db_type(), providing a range of different return values (type, checks). This will look at db_type(), allowing custom model fields to override it.
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
- django.db.models.fields.related.ManyToManyField
▷ def db_returning(self) @property
Private API intended only to be used by Django itself. Currently only the PostgreSQL backend supports returning multiple fields on a model.
@property
def db_returning(self)
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▷ def db_tablespace(self) @property
@property
def db_tablespace(self)
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▶ def db_type(self, connection)
Return the database column data type for this field, for the provided connection.
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Overrides
This method is overriden in:
- django.db.models.fields.related.RelatedField
▷ def db_type_parameters(self, connection)
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▷ def db_type_suffix(self, connection)
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▶ def deconstruct(self)

Return enough information to recreate the field as a 4-tuple:

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* The name of the field on the model, if contribute_to_class() has
   been run.
 * The import path of the field, including the class:e.g.
   django.db.models.IntegerField This should be the most portable
   version, so less specific may be better.
 * A list of positional arguments.
 * A dict of keyword arguments.

Note that the positional or keyword arguments must contain values of
the following types (including inner values of collection types):

 * None, bool, str, int, float, complex, set, frozenset, list, tuple,
   dict
 * UUID
 * datetime.datetime (naive), datetime.date
 * top-level classes, top-level functions - will be referenced by their
   full import path
 * Storage instances - these have their own deconstruct() method

This is because the values here must be serialized into a text format
(possibly new Python code, possibly JSON) and these are the only types
with encoding handlers defined.

There's no need to return the exact way the field was instantiated this
time, just ensure that the resulting field is the same - prefer keyword
arguments over positional ones, and omit parameters with their default
values.

Overrides

This method is overriden in:

▶ def formfield(self, form_class=None, choices_form_class=None, **kwargs)
Return a django.forms.Field instance for this field.
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Overrides
This method is overriden in:
▶ def get_attname(self)
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
▶ def get_attname_column(self)
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignObject
▶ def get_choices(self, include_blank=True, blank_choice=BLANK_CHOICE_DASH, ...)
Return choices with a default blank choices included, for use as <select> choices for this field.
def get_choices(
self,
include_blank=True,
blank_choice=BLANK_CHOICE_DASH,
limit_choices_to=None,
ordering=(),
)
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▶ def get_col(self, alias, output_field=None)
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
▶ def get_db_converters(self, connection)
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
- django.db.models.fields.DurationField
▶ def get_db_prep_save(self, value, connection)
Return field's value prepared for saving into a database.
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
- django.db.models.fields.DecimalField
▶ def get_db_prep_value(self, value, connection, prepared=False)
Return field's value prepared for interacting with the database backend.
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```
Used by the default implementations of get_db_prep_save().
```
Overrides
This method is overriden in:
▶ def get_default(self)
Return the default value for this field.
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
- django.db.models.fields.BinaryField
▷ def get_filter_kwargs_for_object(self, obj)
Return a dict that when passed as kwargs to self.model.filter(), would yield all instances having the same value for this field as obj has.
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▶ def get_internal_type(self)
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Overrides
This method is overriden in:

▶ def get_pk_value_on_save(self, instance)

Hook to generate new PK values on save. This method is called when

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saving instances with no primary key value set. If this method returns
something else than None, then the returned value is used when saving
the new instance.

▶ def get_prep_value(self, value)
Perform preliminary non-db specific value checks and conversions.
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Overrides
This method is overriden in:
▷ def has_default(self)
Return a boolean of whether this field has a default value.
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▶ def pre_save(self, model_instance, add)
Return field's value just before saving.
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Overrides
This method is overriden in:
▶ def rel_db_type(self, connection)
Return the data type that a related field pointing to this field should use. For example, this method is called by ForeignKey and OneToOneField to determine its data type.
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Overrides
This method is overriden in:
▷ def run_validators(self, value)
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▶ def save_form_data(self, instance, data)
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Overrides
This method is overriden in:
▷ def select_format(self, compiler, sql, params)
Custom format for select clauses. For example, GIS columns need to be selected as AsText(table.col) on MySQL as the table.col data can't be used by Django.
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▷ def set_attributes_from_name(self, name)
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▶ def to_python(self, value)
Convert the input value into the expected Python data type, raising django.core.exceptions.ValidationError if the data can't be converted. Return the converted value. Subclasses should override this.
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Overrides
This method is overriden in:
▷ def unique(self) @property
@property
def unique(self)
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▶ def validate(self, value, model_instance)
Validate value and raise ValidationError if necessary. Subclasses should override this to provide validation logic.
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Overrides
This method is overriden in:
- django.db.models.fields.related.ForeignKey
- django.db.models.fields.json.JSONField
▶ def validators(self) @cached_property
Some validators can't be created at field initialization time. This method provides a way to delay their creation until required.
@cached_property
def validators(self)
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Overrides
This method is overriden in:
- django.db.models.fields.DecimalField
- django.db.models.fields.IntegerField
▶ def value_from_object(self, obj)
Return the value of this field in the given model instance.
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Overrides
This method is overriden in:
- django.db.models.fields.related.ManyToManyField
▶ def value_to_string(self, obj)
Return a string value of this field from the passed obj. This is used by the serialization framework.
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Overrides
This method is overriden in:

Inherited methods

Methods inherited from django.db.models.query_utils.RegisterLookupMixin:
get_lookup, get_lookups, get_transform, merge_dicts, register_lookup

Subclasses

Reexports

Imported in django.db.models.lookups.
Imported in django.db.models.sql.query.
Imported in django.db.models.functions.datetime.
Imported in django.db.models.fields.related.
Imported in django.db.models.fields.json.
Imported in django.db.models.fields.files.

Django

Class Field

Declaration

Documentation

Methods

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