Applications (objetto.applications)

An objetto.applications.Application oversees all objetto.bases.BaseObject objects that are meant to work together. It provides different contexts for managing and keeping track of their changes.

Objects that are part of different applications see each other as regular values and can never be part of the same hierarchy.

An application can have root objects defined by objetto.applications.root(), which are always available at the top of the hierarchy, and cannot be parented under other objects.

Application Class

class objetto.applications.ApplicationMeta(name, bases, dct)

Metaclass for objetto.applications.Application.

Inherits from:

objetto.bases.BaseMeta

Features:

Check and store root descriptors.

property _roots

Attributes mapped by name.

Return type: dict[str, objetto.applications.ApplicationRoot]

property _root_names

Names mapped by root.

Return type: dict[objetto.applications.ApplicationRoot, str]

class objetto.applications.Application

Application.

Metaclass:

objetto.applications.ApplicationMeta

Inherits from:

objetto.bases.Base

Features:

Manages multiple objetto.bases.BaseObject under the same hierarchy.
Offers contexts for reading/writing/batch.
Reverts changes when an error occurs.
Manages objetto.objects.Action propagation, internally and externally.

When initializing an objetto.objects.BaseObject, you have to pass an objetto.applications.Application as its first parameter.

>>> from objetto import Application, Object

>>> app = Application()
>>> obj = Object(app)  # pass application as first parameter
>>> obj.app is app  # access it through the 'app' property
True

_get_property(prop, **kwargs)

Get property value.

Parameters

prop (objetto.applications.ApplicationProperty) – Application property.
kwargs – Keyword arguments to be passed to the default factory.

Returns

Value.

Raises

TypeError – Invalid parameter type.

_set_property(prop, value)

Set property value.

Parameters

prop (objetto.applications.ApplicationProperty) – Application property.
value – Value.

Raises

TypeError – Invalid parameter type.

_delete_property(prop, force=False)

Delete property value.

Parameters

prop (objetto.applications.ApplicationProperty) – Application property.
force (bool) – If True, will not fail if has no value set.

Raises

TypeError – Invalid parameter type.
ValueError – Property has no value.

read_context(snapshot=None)

Read context.

Parameters: snapshot (objetto.applications.ApplicationSnapshot) – Application state snapshot.
Returns: Context manager.
Return type: contextlib.AbstractContextManager
Raises: ValueError – Application mismatch.

write_context()

Write context.

Returns: Context manager.
Return type: contextlib.AbstractContextManager

temporary_context()

Temporary write context.

Returns: Context manager.
Return type: contextlib.AbstractContextManager

take_snapshot()

Take a snapshot of the current application state.

Returns: Application snapshot.
Return type: objetto.applications.ApplicationSnapshot

property is_writing

Whether this application is inside a write context.

Return type: bool

property is_reading

Whether this application is inside a read context.

Return type: bool

Root Descriptor

objetto.applications.root(obj_type, priority=None, **kwargs)

Describes a root object that gets initialized with the application.

>>> from objetto import Application, Object, attribute, root

>>> class MyObject(Object):
...     name = attribute(str)
...
>>> class MyApplication(Application):  # subclass for adding roots
...     root_a = root(MyObject, name="Root A")  # describe root
...     root_b = root(MyObject, name="Root B")  # describe root
...
>>> app = MyApplication()  # instantiate the application
>>> app.root_a  # access a root object
MyObject(name='Root A')

Parameters

obj_type (type[objetto.bases.BaseObject]) – Object type.
priority (int or None) – Initialization priority.
kwargs – Keyword arguments to be passed to the object’s __init__.

Returns

Application root descriptor.

Return type

objetto.applications.ApplicationRoot

Raises

ValueError – Used reserved keyword argument.
TypeError – Invalid object type.

Root Descriptor Class

class objetto.applications.ApplicationRoot(obj_type, priority=None, **kwargs)

Describes a root object that gets initialized with the application.

Note

Prefer using the objetto.applications.root() factory over instantiating objetto.applications.ApplicationRoot directly.

Inherits from:

objetto.bases.Base

Parameters

obj_type (type[objetto.bases.BaseObject]) – Object type.
priority (int or None) – Initialization priority.
kwargs – Keyword arguments to be passed to the object’s __init__.

Raises

ValueError – Used reserved keyword argument.
TypeError – Invalid object type.

__get__(instance, owner)

Get attribute value when accessing from valid instance or this descriptor otherwise.

Parameters

instance (objetto.applications.Application or None) – Instance.
owner (type[objetto.applications.Application]) – Owner class.

Returns

Object instance or this descriptor.

Return type

objetto.bases.BaseObject or objetto.applications.ApplicationRoot

__hash__()

Get hash based on object id.

Returns: Hash based on object id.
Return type: int

__eq__(other)

Compare with another object for identity.

Parameters: other – Another object.
Returns: True if the same object.
Return type: bool

__repr__()

Get representation.

Returns: Representation.
Return type: str

to_dict()

Convert to dictionary.

Returns: Dictionary.
Return type: dict[str, Any]

property obj_type

Object type.

Return type: type[objetto.bases.BaseObject]

property priority

Initialization priority.

Return type: int or None

property kwargs: Keyword arguments to be passed to object’s ‘__init__’.

Application Property Class

class objetto.applications.ApplicationProperty(default_factory=None, module=None)

Dynamic generic application property.

Inherits from:

objetto.bases.Base

Parameters: default_factory (str or collections.abc.Callable or None) – Default value factory.

fabricate_default_value(**kwargs)

Fabricate default value.

Parameters: kwargs – Keyword arguments to be passed to the factory.
Returns: Fabricated value.
Raises: ValueError – No default factory.

property default_factory

Default value factory.

Return type: str or collections.abc.Callable or None

property module

Optional module path to use in case partial paths are provided.

Return type: str or None

Application Snapshot Class

class objetto.applications.ApplicationSnapshot(app, storage)

Application snapshot.

Inherits from:

objetto.bases.Base

Features:

Freezes entire application state at a moment in time.
Can be used with an application’s read context to travel back in time.

You can acquire a snapshot by calling the objetto.applications.Application.take_snapshot() method. You can then pass it to a objetto.applications.Application.read_context() in order to temporarily bring the whole application back to the time the snapshot was taken.

>>> from objetto import Application, Object, attribute

>>> class Person(Object):
...     name = attribute(str)
...
>>> app = Application()
>>> obj = Person(app, name="Albert")
>>> obj.name
'Albert'
>>> snapshot = app.take_snapshot()
>>> obj.name = "Einstein"
>>> obj.name
'Einstein'
>>> with app.read_context(snapshot):
...     obj.name
...
'Albert'
>>> obj.name
'Einstein'

property app

Application.

Return type: objetto.applications.Application