On Sun, 03 Sep 2006 16:29:11 +0200, Bruno Desthuilliers <[EMAIL PROTECTED]> wrote: >Paul Rubin a écrit : >> Bruno Desthuilliers <[EMAIL PROTECTED]> writes: >> >>>I've rarely encoutered "silent" data corruption with Python - FWIW, I >>>once had such a problem, but with a lower-level statically typed >>>language (integer overflow), and I was a very newbie programmer by that >>>time. Usually, one *very quickly* notices when something goes wrong. >> >> >> The same thing can happen in Python, and the resulting bugs can be >> pretty subtle. I noticed the following example as the result of >> another thread, which was about how to sort an 85 gigabyte file. >> Try to put a slice interface on a file-based object and you can >> hit strange integer-overflow bugs once the file gets larger than 2GB: >> >> Python 2.3.4 (#1, Feb 2 2005, 12:11:53) >> [GCC 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)] on linux2 >> Type "help", "copyright", "credits" or "license" for more information. >> >>> print slice(0, 3**33) >> slice(0, 5559060566555523L, None) # OK ... >> >> So we expect slicing with large args to work properly. But then: >> >> >>> class A: >> ... def __getitem__(self, s): >> ... print s >> ... >> >>> a = A() >> >>> a[0:3**33] >> slice(0, 2147483647, None) # oops!!!! >> >>> > >Looks like a Python bug, not a programmer error. And BTW, it doesn't >happens with >=2.4.1 > >Python 2.4.1 (#1, Jul 23 2005, 00:37:37) >[GCC 3.3.4 20040623 (Gentoo Linux 3.3.4-r1, ssp-3.3.2-2, pie-8.7.6)] on >linux2 >Type "help", "copyright", "credits" or "license" for more information. > >>> print slice(0, 3**33) >slice(0, 5559060566555523L, None) > >>> class A(object): >... def __getitem__(self, s): >... print s >... > >>> A()[0:3**33] >slice(0, 5559060566555523L, None) > >>>
Note that it _does_ happen with current [EMAIL PROTECTED]: Python 2.6a0 (trunk:51698M, Sep 3 2006, 12:40:55) [GCC 4.0.3 (Ubuntu 4.0.3-1ubuntu5)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> slice(0, 3 ** 33) slice(0, 5559060566555523L, None) >>> class x: ... def __getitem__(self, idx): print idx ... >>> x()[:3**33] slice(0, 2147483647, None) >>> Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
