dispatch Package

dispatch Package

saferef Module

“Safe weakrefs”, originally from pyDispatcher.

Provides a way to safely weakref any function, including bound methods (which aren’t handled by the core weakref module).

class thriftpool.utils.dispatch.saferef.BoundMethodWeakref(target, on_delete=None)

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.

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

_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)

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.

class thriftpool.utils.dispatch.saferef.BoundNonDescriptorMethodWeakref(target, on_delete=None)

Bases: thriftpool.utils.dispatch.saferef.BoundMethodWeakref

A specialized BoundMethodWeakref, for platforms where instance methods are not descriptors.

It assumes that the function name and the target attribute name are the same, instead of assuming that the function is a descriptor. This approach is equally fast, but not 100% reliable because functions can be stored on an attribute named differenty than the function’s name such as in:

>>> class A(object):
...     pass

>>> def foo(self):
...     return "foo"
>>> A.bar = foo

But this shouldn’t be a common use case. So, on platforms where methods aren’t descriptors (such as Jython) this implementation has the advantage of working in the most cases.

thriftpool.utils.dispatch.saferef.get_bound_method_weakref(target, on_delete)

Instantiates the appropiate BoundMethodWeakRef, depending on the details of the underlying class method implementation.

thriftpool.utils.dispatch.saferef.safe_ref(target, on_delete=None)

Return a safe weak reference to a callable target

Parameters:

• target – the object to be weakly referenced, if it’s a bound method reference, will create a BoundMethodWeakref, otherwise creates a simple weakref.ref.
• 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.ref or a BoundMethodWeakref) as argument.

signal Module

Signal class.

class thriftpool.utils.dispatch.signal.Signal(providing_args=None)

Bases: object

Base class for all signals

receivers

Internal attribute, holds a dictionary of

`{receriverkey (id): weakref(receiver)}` mappings.

connect(*args, **kwargs)

Connect receiver to sender for signal.

Parameters:

• receiver –

  A function or an instance method which is to receive signals. Receivers must be hashable objects.

  if weak is True, then receiver must be weak-referencable (more precisely saferef.safe_ref() must be able to create a reference to the receiver).

  Receivers must be able to accept keyword arguments.

  If receivers have a dispatch_uid attribute, the receiver will not be added if another receiver already exists with that dispatch_uid.

• sender – The sender to which the receiver should respond. Must either be of type Signal, or None to receive events from any sender.
• weak – Whether to use weak references to the receiver. By default, the module will attempt to use weak references to the receiver objects. If this parameter is false, then strong references will be used.
• dispatch_uid – An identifier used to uniquely identify a particular instance of a receiver. This will usually be a string, though it may be anything hashable.

disconnect(receiver=None, sender=None, weak=True, dispatch_uid=None)

Disconnect receiver from sender for signal.

If weak references are used, disconnect need not be called. The receiver will be removed from dispatch automatically.

Parameters:

• receiver – The registered receiver to disconnect. May be none if dispatch_uid is specified.
• sender – The registered sender to disconnect.
• weak – The weakref state to disconnect.
• dispatch_uid – the unique identifier of the receiver to disconnect

send(sender, **named)

Send signal from sender to all connected receivers.

If any receiver raises an error, the error propagates back through send, terminating the dispatch loop, so it is quite possible to not have all receivers called if a raises an error.

Parameters:

• sender – The sender of the signal. Either a specific object or None.
• **named – Named arguments which will be passed to receivers.

Returns:

a list of tuple pairs: [(receiver, response), ... ].

send_robust(sender, **named)

Send signal from sender to all connected receivers catching errors.

Parameters:

• sender – The sender of the signal. Can be any python object (normally one registered with a connect if you actually want something to occur).
• **named – Named arguments which will be passed to receivers. These arguments must be a subset of the argument names defined in providing_args.

Returns:

a list of tuple pairs: [(receiver, response), ... ].

Raises DispatcherKeyError:  

if any receiver raises an error (specifically any subclass of Exception), the error instance is returned as the result for that receiver.