sugar.dispatch package

Submodules

sugar.dispatch.dispatcher module

class sugar.dispatch.dispatcher.Signal(providing_args=None)

Bases: object

Base class for all signals

Internal attributes:

receivers – { receriverkey (id) : weakref(receiver) }

__init__(providing_args=None)

providing_args – A list of the arguments this signal can pass along in a send() call.

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

Connect receiver to sender for signal

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.safeRef() 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.

returns None

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

Disconnect receiver from sender for signal

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

disconnect reverses the process of connect.

If weak references are used, disconnect need not be called.

The receiver will be remove from dispatch automatically.

returns None

send(sender, **named)

Send signal from sender to all connected receivers.

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), … ].

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.

send_robust(sender, **named)

Send signal from sender to all connected receivers catching errors

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.

Return a list of tuple pairs [(receiver, response), … ], may raise DispatcherKeyError

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

sugar.dispatch.dispatcher.im_self(func)

sugar.dispatch.dispatcher.im_func(func)

sugar.dispatch.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).

sugar.dispatch.saferef.safeRef(target, onDelete=None)

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.

onDelete – 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.

class sugar.dispatch.saferef.BoundMethodWeakref(target, onDelete=None, *arguments, **named)

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 calculateKey method applied to the target instance method

deletionMethods -- 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 onDelete parameters of safeRef calls.

weakSelf -- weak reference to the target object

weakFunc -- weak reference to the target function

Class Attributes:

_allInstances – class attribute pointing to all live

BoundMethodWeakref objects indexed by the class’s calculateKey(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.

static __new__(cls, target, onDelete=None, *arguments, **named)

Create new instance or return current instance

Basically this method of construction allows us to short-circuit creation of references to already- referenced instance methods. The key corresponding to the target is calculated, and if there is already an existing reference, that is returned, with its deletionMethods attribute updated. Otherwise the new instance is created and registered in the table of already-referenced methods.

__init__(target, onDelete=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:

target.im_func.__get__( target.im_self )

which is true of built-in instance methods.

onDelete – 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.

classmethod calculateKey(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.

__str__()

Give a friendly representation of the object

__repr__()

Give a friendly representation of the object

__bool__()

Whether we are still a valid reference

__nonzero__()

Python2 alternative for __bool__

__cmp__(other)

Compare with another reference

__call__()

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.

class sugar.dispatch.saferef.BoundNonDescriptorMethodWeakref(target, onDelete=None, *arguments, **named)

Bases: 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: 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.

__init__(target, onDelete=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:

target.im_func.__get__( target.im_self )

which is true of built-in instance methods.

onDelete – 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.

__call__()

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.

sugar.dispatch.saferef.get_bound_method_weakref(target, onDelete)

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

sugar.dispatch.saferef.im_self(func)

sugar.dispatch.saferef.im_func(func)

Module contents

Multi-consumer multi-producer dispatching mechanism

Originally based on pydispatch (BSD) http://pypi.python.org/pypi/PyDispatcher/2.0.1 See license.txt for original license.

Heavily modified for Django’s purposes.