Model _meta API¶
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class
Options¶
The model _meta API is at the core of the Django ORM. It enables other
parts of the system such as lookups, queries, forms, and the admin to
understand the capabilities of each model. The API is accessible through
the _meta attribute of each model class, which is an instance of an
django.db.models.options.Options object.
Methods that it provides can be used to:
- Retrieve all field instances of a model
- Retrieve a single field instance of a model by name
Field access API¶
Retrieving a single field instance of a model by name¶
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Options.get_field(field_name)¶ Returns the field instance given a name of a field.
field_namecan be the name of a field on the model, a field on an abstract or inherited model, or a field defined on another model that points to the model. In the latter case, thefield_namewill be (in order of preference) therelated_query_nameset by the user, therelated_nameset by the user, or the name automatically generated by Django.Hidden fieldscannot be retrieved by name.If a field with the given name is not found a
FieldDoesNotExistexception will be raised.>>> from django.contrib.auth.models import User # A field on the model >>> User._meta.get_field('username') <django.db.models.fields.CharField: username> # A field from another model that has a relation with the current model >>> User._meta.get_field('logentry') <ManyToOneRel: admin.logentry> # A non existent field >>> User._meta.get_field('does_not_exist') Traceback (most recent call last): ... FieldDoesNotExist: User has no field named 'does_not_exist'
Retrieving all field instances of a model¶
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Options.get_fields(include_parents=True, include_hidden=False)¶ Returns a tuple of fields associated with a model.
get_fields()accepts two parameters that can be used to control which fields are returned:include_parentsTrueby default. Recursively includes fields defined on parent classes. If set toFalse,get_fields()will only search for fields declared directly on the current model. Fields from models that directly inherit from abstract models or proxy classes are considered to be local, not on the parent.include_hiddenFalseby default. If set toTrue,get_fields()will include fields that are used to back other field’s functionality. This will also include any fields that have arelated_name(such asManyToManyField, orForeignKey) that start with a „+”.
>>> from django.contrib.auth.models import User >>> User._meta.get_fields() (<ManyToOneRel: admin.logentry>, <django.db.models.fields.AutoField: id>, <django.db.models.fields.CharField: password>, <django.db.models.fields.DateTimeField: last_login>, <django.db.models.fields.BooleanField: is_superuser>, <django.db.models.fields.CharField: username>, <django.db.models.fields.CharField: first_name>, <django.db.models.fields.CharField: last_name>, <django.db.models.fields.EmailField: email>, <django.db.models.fields.BooleanField: is_staff>, <django.db.models.fields.BooleanField: is_active>, <django.db.models.fields.DateTimeField: date_joined>, <django.db.models.fields.related.ManyToManyField: groups>, <django.db.models.fields.related.ManyToManyField: user_permissions>) # Also include hidden fields. >>> User._meta.get_fields(include_hidden=True) (<ManyToOneRel: auth.user_groups>, <ManyToOneRel: auth.user_user_permissions>, <ManyToOneRel: admin.logentry>, <django.db.models.fields.AutoField: id>, <django.db.models.fields.CharField: password>, <django.db.models.fields.DateTimeField: last_login>, <django.db.models.fields.BooleanField: is_superuser>, <django.db.models.fields.CharField: username>, <django.db.models.fields.CharField: first_name>, <django.db.models.fields.CharField: last_name>, <django.db.models.fields.EmailField: email>, <django.db.models.fields.BooleanField: is_staff>, <django.db.models.fields.BooleanField: is_active>, <django.db.models.fields.DateTimeField: date_joined>, <django.db.models.fields.related.ManyToManyField: groups>, <django.db.models.fields.related.ManyToManyField: user_permissions>)
