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Google App Engine

Metadata Entities Python Reference

The model classes Namespace, Kind, and Property define the special entity kinds returned as the results of metadata queries. These classes are all defined in the package google.appengine.ext.db.metadata. See the page Metadata Queries for more information and examples of their use.

Helper Functions

The following helper functions are available for obtaining metadata information without issuing an explicit query:

get_namespaces(start=None, end=None)

Returns a list of namespace names.

Arguments

start

If not None, return only namespace names greater than or equal to the specified value.

end

If not None, return only namespace names less than the specified value.

get_kinds(start=None, end=None)

Returns a list of entity kind names.

Arguments

start

If not None, return only kind names greater than or equal to the specified value.

end

If not None, return only kind names less than the specified value.

get_properties_of_kind(kind, start=None, end=None)

Returns a list of indexed property names for a specified kind. Unindexed properties are not included.

Arguments

kind

The kind whose property names are requested.

start

If not None, return only property names greater than or equal to the specified value.

end

If not None, return only property names less than the specified value.

get_representations_of_kind(kind, start=None, end=None)

Returns a dictionary mapping each indexed property name for a specified kind to a list of its representations. Unindexed properties are not included.

Arguments

kind

The kind whose property representations are requested.

start

If not None, return only representations for properties whose names are greater than or equal to the specified value.

end

If not None, return only representations for properties whose names are less than the specified value.

The Namespace Class

Class Namespace represents a metadata entity of the special kind __namespace__, returned as a result of a namespace query. The entity's key is the name of the namespace. (An exception is the default namespace designated by the empty string "": since this is not a valid key name, the default namespace is represented by a key with numeric ID 1 instead.)

Property

Instances of class Namespace have the following property:

namespace_name

Returns the name of the namespace specified by this entity's key.

Class Methods

Class Namespace has the following class methods:

key_for_namespace(namespace)

Returns the __namespace__ key for the specified namespace.

Argument

namespace

The namespace whose key is requested.

key_to_namespace(key)

Returns the namespace specified by a given __namespace__ key.

Argument

key

The key whose name is requested.

The Kind Class

Class Kind represents a metadata entity of the special kind __kind__, returned as a result of a kind query. The entity's key is the name of the entity kind.

Property

Instances of class Kind have the following property:

kind_name

Returns the kind name specified by this entity's key.

Class Methods

Class Kind has the following class methods:

key_for_kind(kind)

Returns the __kind__ key for the specified kind.

Argument

kind

The kind whose key is requested.

key_to_kind(key)

Returns the kind specified by a given __kind__ key.

Argument

key

The key whose kind is requested.

The Property Class

Class Property represents a metadata entity of the special kind __property__, returned as a result of a property query. The entity representing property P of kind K is built as follows:

  • The entity's key has kind __property__ and key name P.
  • The parent entity's key has kind __kind__ and key name K.

Properties

Instances of class Property have the following properties:

kind_name

Returns the property name specified by this entity's key.

property_name

Returns the property name specified by this entity's key.

Class Methods

Class Property has the following class methods:

key_for_kind(kind)

Returns the parent key for __property__ keys of the specified kind.

Argument

kind

The kind whose parent key is requested.

key_for_property(kind, property)

Returns the __property__ key for the specified property and kind.

Arguments

kind

The kind whose key is requested.

property

The property whose key is requested.

key_to_kind(key)

Returns the kind specified by a given __property__ key.

Argument

key

The key whose kind name is requested.

key_to_property(key)

Returns the property specified by a given __property__ key, or None if the key specified only a kind.

Argument

key

The key whose property name is requested.