[issue1407] [performance] Too many closed() checkings

[Guido van Rossum]

Guido van Rossum added the comment:

To find out what really happens, use pdb to step through the example.
This gives much better insight than adding a printf() call to
PyObject_Call(). I've notice myself when stepping through I/O that there
are a lot of checks for closed -- this may have to do with the stacking
text -> buffer -> binary though. I've also noticed overridden isinstance
checks in abc.py being called, which surprised me slightly. I haven't
had time to look into this further though.

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nosy: +gvanrossum

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