Hey Antoine,
Thanks for the clarification!
I see that the C implementation matches the Python implementation but I
don't see how the semantics of either are useful in this case.
If a subclass implements flush then, as you say, it must also implement
close and call flush itself before calling its superclass' close method.
But then _RawIOBase will pointlessly call the subclass' flush method a
second time. This second call should raise (because the file is closed)
and the exception will be caught and suppressed.
I don't see why this is helpful. Could you explain why
_RawIOBase.close() calling self.flush() is useful?
Cheers,
Brian
Antoine Pitrou wrote:
Hi!
<brian <at> sweetapp.com> writes:
class _RawIOBase(_FileIO):
FileIO is a subclass of _RawIOBase, not the reverse:
issubclass(_io._RawIOBase, _io.FileIO)
False
issubclass(_io.FileIO, _io._RawIOBase)
True
I do understand your surprise, but the Python implementation of IOBase.close()
in _pyio.py does the same thing:
def close(self) -> None:
"""Flush and close the IO object.
This method has no effect if the file is already closed.
"""
if not self.__closed:
try:
self.flush()
except IOError:
pass # If flush() fails, just give up
self.__closed = True
Note how it calls `self.flush()` and not `IOBase.flush(self)`.
When writing the C version of the I/O stack, we tried to keep the semantics the
same as in the Python version, although there are a couple of subtleties.
Your problem here is that it's IOBase.close() which calls your flush() method,
but FileIO.close() has already done its job before and the internal file
descriptor has been closed (hence `self.closed` is True). In this particular
case, I advocate overriding close() as well and call your flush() method
manually from there.
Thanks for your feedback!
Regards
Antoine.
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/brian%40sweetapp.com
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
