BoundMethodWeakref
'Safe' and reusable weak references to instance methods.
The BoundMethodWeakref class is accessible via the louie.saferef module.
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.
Methods
f __init__(self, target, on_delete=None) ...
Return a weak-reference-like instance for a bound method.
-
target: The instance-method target for the weak reference, must have im_self and im_func attributes and be reconstructable via the following, which is true of built-in instance methods:
target.im_func.__get__( target.im_self )
-
on_delete: Optional callback which will be called when this weak reference ceases to be valid (i.e. either the object or the function is garbage collected). Should take a single argument, which will be passed a pointer to this object.
f calculate_key(cls, target) ...
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.
f __call__(self) ...
Return a strong reference to the bound method.
If the target cannot be retrieved, then will return None, otherwise returns a bound instance method for our object and function.
Note: You may call this method any number of times, as it does not invalidate the reference.
See the source for more information.