[Python-ideas] breaking cycles that include __del__

[Antoine Pitrou]

Daniel Stutzbach <daniel at ...> writes:
> 
> Unfortunately, if the object ends up in a cycle, then the recipe can't do
> its job because __del__ will never be called.

You don't need __del__, a weakref is good enough since you only need to remember
an adequate string representation of the object:

class Widget:
  closed = False

  def __init__(self):
    # ...
    def error_not_closed(_, r=repr(self)):
      log_an_error('%s not closed properly' % r)
    self._wr_not_closed = weakref.ref(self, error_not_closed)

  def close(self):
    if self.closed: return
    self.closed = True
    # Destroy weakref
    self._wr_not_closed = None
    # Free various resources from ctypes, etc.


Regards

Antoine.