[Python-3000] PEP: Eliminate del (original) (raw)

Raymond Hettinger python at rcn.com
Fri May 4 17:22:45 CEST 2007

[Michael Bayer]

why not encapsulate the "proper" weakref-based approach in an easy-to- use method such as "close()" ? that way nobody has to guess how to follow this pattern.

An encapsulating function should be added to the weakref module so that Guido's example could be written as:

class BufferedWriter:

def init(self, raw): self.raw = raw self.buffer = "" weakref.cleanup(self, lambda s: s.raw.write(s.buffer))

def write(self, data): self.buffer += data if len(self.buffer) >= 8192: self.flush()

def flush(self): self.raw.write(self.buffer) self.buffer = ""

I've got a first cut at an encapsulating function but am not happy with it yet. There is almost certainly a better way. First draft:

def cleanup(obj, callback, _reg = []): class AttrMap(object): def init(self, map): self._map = map def getattr(self, key): return self._map[key]
def wrapper(wr, mp=AttrMap(obj.dict), callback=callback): _reg.remove(wr) callback(mp) _reg.append(ref(obj, wrapper))

Raymond

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