Benjamin Peterson <benja...@python.org> writes: > On Thu, Jun 12, 2014, at 18:06, Nikolaus Rath wrote: >> Consider this simple example: >> >> $ cat test.py >> import io >> import warnings >> >> class StridedStream(io.IOBase): >> def __init__(self, name, stride=2): >> super().__init__() >> self.fh = open(name, 'rb') >> self.stride = stride >> >> def read(self, len_): >> return self.fh.read(self.stride*len_)[::self.stride] >> >> def close(self): >> self.fh.close() >> >> class FixedStridedStream(StridedStream): >> def __del__(self): >> # Prevent IOBase.__del__ frombeing called. >> pass >> >> warnings.resetwarnings() >> warnings.simplefilter('error') >> >> print('Creating & loosing StridedStream..') >> r = StridedStream('/dev/zero') >> del r >> >> print('Creating & loosing FixedStridedStream..') >> r = FixedStridedStream('/dev/zero') >> del r >> >> $ python3 test.py >> Creating & loosing StridedStream.. >> Creating & loosing FixedStridedStream.. >> Exception ignored in: <_io.FileIO name='/dev/zero' mode='rb'> >> ResourceWarning: unclosed file <_io.BufferedReader name='/dev/zero'> >> >> In the first case, the destructor inherited from IOBase actually >> prevents the ResourceWarning from being emitted. > > Ah, I see. I don't see any good ways to fix it, though, besides setting > some flag if close() is called from __del__.
How about not having IOBase.__del__ call self.close()? Any resources acquired by the derived class would still clean up after themselves when they are garbage collected. Best, -Nikolaus -- GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.« _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com