session: Application session support

A session provides access to most of the application’s state. At a minimum, it does not include the operating system state, like the current directory, nor the environment, nor any Python interpreter state – e.g., the exception hook, module globals, etc.

Code should be designed to support multiple sessions per process since it is easier to start with that assumption rather than add it later. Possible uses of multiple sessions include: one session per tabbed graphics window, or for comparing two sessions.

Session data, ie., data that is archived, uses the State and StateManager API.


session file suffix

class Session(app_name, *, debug=False, silent=False, minimal=False)

Bases: object

Supported API. Session management

The metadata attribute should be a dictionary with information about the session, e.g., a thumbnail, a description, the author, etc. See standard_metadata().

Attributes that support the StateManager API are automatically added as state managers (e.g. the session’s add_state_manager method is called with the ‘tag’ argument the same as the attribute name). Conversely, deleting the attribute will call remove_state_manager. If a session attribute is not desired, the add/remove_state_manager methods can be called directly.

loggerAn instance of Logger

Used to log information, warning, errors.


Information kept at beginning of session file, eg., a thumbnail

modelsInstance of Models.
triggersAn instance of TriggerSet

Starts with session triggers.

main_viewAn instance of View

Default view.

metadata = None

Experimental API . session metadata


Experimental API . Reset session to data-less state

restore(self, stream, path=None, resize_window=None, restore_camera=True, metadata_only=False)

Experimental API . Deserialize session from binary stream.

save(self, stream, version, include_maps=False)

Experimental API . Serialize session to binary stream.

snapshot_methods(self, obj, instance=True, base_type=<class 'chimerax.core.state.State'>)

Experimental API . Return an object having take_snapshot(), restore_snapshot(), and reset_state() methods for the given object. Can return None if no save/restore methods are available, for instance for primitive types.

class UserAliases

Bases: StateManager

reset_state(self, session)

Experimental API . Reset state to data-less state

classmethod restore_snapshot(session, data)

Experimental API . Create object using snapshot data.

take_snapshot(self, session, flags)

Experimental API . Return snapshot of current state of instance.

The semantics of the data is unknown to the caller. Returns None if should be skipped. The default implementation is for non-core classes and returns a copy of the instance dictionary (a deep copy of lists/dicts/etc., but shallow copy of named objects). Named objects are later converted to unique names.


Experimental API . Initialize session with common data containers


Experimental API . Session save gui options are registered in the ui module instead of when the format is registered because the ui does not exist when the format is registered.

save(session, path, version=3, uncompressed=False, include_maps=False)

Experimental API . command line version of saving a session

sdump(session, session_file, output=None)

Experimental API . dump contents of session for debugging


Experimental API . Fill in standard metadata for created files


Optional dictionary of previous metadata.

The standard metadata consists of:
generator :

Application that created file in HTML User Agent format (app name version (os))

created :

Date first created

modified :

Date last modified after being created

creator :

User name(s)

dateCopyrighted :


creator and dateCopyrighted can be lists if there
is previous metadata with different values.
Dates are in ISO 8601 UTC time. Also see
Metadata names are inspired by the HTML5 metadata,