The model classes EntityGroup , Namespace , Kind , and Property represent the results of getting or querying metadata kinds. These classes are all defined in the package google.appengine.ext.db.metadata . See the page Metadata for more information and examples of their use.

1. Helper Functions
• get_entity_group_version
• get_namespaces
• get_kinds
• get_properties_of_kind
• get_representations_of_kind
2. EntityGroup
• Property
• version
• Class Method
• key_for_entity
3. Namespace
• Property
• namespace_name
• Class Methods
• key_for_namespace
• key_to_namespace
4. Kind
• Property
• kind_name
• Class Methods
• key_for_kind
• key_to_kind
5. Property
• Properties
• kind_name
• property_name
• Class Methods
• key_for_kind
• key_for_property
• key_to_kind
• key_to_property

Helper Functions

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

get_entity_group_version ( entity_or_key )

Returns the version of the entity group containing entity_or_key . This version is guaranteed to increase on every change to the entity group. The version may increase even in the absence of user-visible changes to the entity group. May return None if the entity group was never written to. On non-HR datatores, this function returns None .

Arguments:

entity_or_key

a key or entity whose version you want.

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 EntityGroup Class

Model for __entity_group__ metadata (available in HR datastore only).

This metadata contains a numeric __version__ property that is guaranteed to increase on every change to the entity group. The version may increase even in the absence of user-visible changes to the entity group. The __entity_group__ entity may not exist if the entity group was never written to.

Property

version

The version number

Class Method

key_for_entity ( entity_or_key )

Return the metadata key for the entity group containing entity_or_key . Use this key as the argument to get() the __entity_group__ metadata entity for the entity group containing entity_or_key .

Arguments:

entity_or_key

a key or entity whose __entity_group__ key you want.

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.

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