Python supports weak references as first-class objects. There are two specific object types which directly implement weak references. The first is a simple reference object, and the second acts as a proxy for the original object as much as it can.
| ob) | 
| ob) | 
| ob) | 
| PyObject *ob, PyObject *callback) | 
None or NULL.  If ob
  is not a weakly-referencable object, or if callback is not
  callable, None, or NULL, this will return NULL and
  raise TypeError.
  
New in version 2.2.
| PyObject *ob, PyObject *callback) | 
None or NULL.  If ob is not
  a weakly-referencable object, or if callback is not callable,
  None, or NULL, this will return NULL and raise
  TypeError.
  
New in version 2.2.
| PyObject *ref) | 
None.
  
New in version 2.2.
| PyObject *ref) | 
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