mxcubecore.saferef#

Refactored ‘safe reference from dispatcher.py

Functions

safe_ref(target[, on_delete])

Return a safe weak reference to a callable target.

Classes

BoundMethodWeakref(target[, on_delete])

'Safe' and reusable weak references to instance methods.
class mxcubecore.saferef.BoundMethodWeakref(target, on_delete=None, *arguments, **named)[source]#

Bases: object

‘Safe’ and reusable weak references to instance methods.

BoundMethodWeakref objects provide a mechanism for referencing a bound method without requiring that the method object itself (which is normally a transient object) is kept alive. Instead, the BoundMethodWeakref object keeps weak references to both the object and the function which together define the instance method.

Attributes:

  • key: The identity key for the reference, calculated by the class’s calculate_key method applied to the target instance method.

  • deletion_methods: Sequence of callable objects taking single argument, a reference to this object which will be called when either the target object or target function is garbage collected (i.e. when this object becomes invalid). These are specified as the on_delete parameters of safe_ref calls.

  • weak_self: Weak reference to the target object.

  • weak_func: Weak reference to the target function.

Class Attributes:

  • _all_instances: Class attribute pointing to all live BoundMethodWeakref objects indexed by the class’s calculate_key(target) method applied to the target objects. This weak value dictionary is used to short-circuit creation so that multiple references to the same (object, function) pair produce the same BoundMethodWeakref instance.

classmethod calculate_key(target)[source]#

Calculate the reference key for this reference.

Currently this is a two-tuple of the id()’s of the target object and the target function respectively.

mxcubecore.saferef.safe_ref(target, on_delete=None)[source]#

Return a safe weak reference to a callable target.

  • target: The object to be weakly referenced, if it’s a bound method reference, will create a BoundMethodWeakref, otherwise creates a simple weakref.

  • on_delete: If provided, will have a hard reference stored to the callable to be called after the safe reference goes out of scope with the reference object, (either a weakref or a BoundMethodWeakref) as argument.