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rF t|r4t| | Y S t| Y S Y n:X |dk rt| dspt| dsptd| t| |d}|S dS )a 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.
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d Zdd Z ZS )r a '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.
Nc sd | |}| j|}|dk r.|j| |S tt| | }|| j|< |j||f|| |S dS )a 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 deletion_methods attribute updated.
Otherwise the new instance is created and registered in the
table of already-referenced methods.
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zBoundMethodWeakref.__new__c C sf | fdd}|g| _ | || _t|}t|}t||| _t||| _t || _
t |j | _ dS )a 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.
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zBoundMethodWeakref.__init__c C s t t|t t|fS )zCalculate 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.
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r r r r s z BoundMethodWeakref.calculate_keyc C s d| j j| j| jf S )z-Give a friendly representation of the object.z %s(%s.%s))r" r5 r4 r6 r+ r r r __str__ s
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| dk S )z'Whether we are still a valid reference.Nr r8 r r r __nonzero__ s z BoundMethodWeakref.__nonzero__c C s* t || js t| jt|S t| j|jS )z Compare with another reference.)
isinstancer" Zcmptyper )r+ otherr r r __cmp__ s zBoundMethodWeakref.__cmp__c C s. | }|dk r*| }|dk r*||S dS )a? 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.
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