MRAB <pyt...@mrabarnett.plus.com> writes: > On 2014-06-11 02:30, Nikolaus Rath wrote: >> Hello, >> >> I recently noticed (after some rather protacted debugging) that the >> io.IOBase class comes with a destructor that calls self.close(): >> >> [0] nikratio@vostro:~/tmp$ cat test.py >> import io >> class Foo(io.IOBase): >> def close(self): >> print('close called') >> r = Foo() >> del r >> [0] nikratio@vostro:~/tmp$ python3 test.py >> close called >> >> To me, this came as quite a surprise, and the best "documentation" of >> this feature seems to be the following note (from the io library >> reference): >> >> "The abstract base classes also provide default implementations of some >> methods in order to help implementation of concrete stream classes. For >> example, BufferedIOBase provides unoptimized implementations of >> readinto() and readline()." >> >> For me, having __del__ call close() does not qualify as a reasonable >> default implementation unless close() is required to be idempotent >> (which one could deduce from the documentation if one tries to, but it's >> far from clear). >> >> Is this behavior an accident, or was that a deliberate decision? >> > To me, it makes sense. You want to make sure that it's closed, releasing > any resources it might be holding, even if you haven't done so > explicitly.
I agree with your intentions, but I come to the opposite conclusion: automatically calling close() in the destructor will hide that there's a problem in the code. Without that automatic cleanup, there's at least a good chance that a ResourceWarning will be emitted so the problem gets noticed. "Silently work around bugs in caller's code" doesn't seem like a very useful default to me... 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