Le 02/07/2015 16:52, Steven D'Aprano a écrit :
Despite the title, this is not one of the usual "Why can't Python do maths?" "bug" reports.Can anyone reproduce this behaviour? If so, please reply with the version of Python and your operating system. Printing sys.version will probably do. x = 1 - 1/2**53 assert x == 0.9999999999999999 for i in range(1, 1000000): if int(i*x) == i: print(i); break Using Jython and IronPython, the loop runs to completion. That is the correct behaviour, or so I am lead to believe. Using Python 2.6, 2.7 and 3.3 on Centos and Debian, it prints 2049 and breaks. That should not happen. If you can reproduce that (for any value of i, not necessarily 2049), please reply. See also http://bugs.python.org/issue24546 for more details.
Hi, vincent@tiemoko:~$ python3 Python 3.2.3 (default, Jun 18 2015, 21:46:42) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> x = 1 - 1/2**53 >>> assert x == 0.9999999999999999 >>> for i in range(1, 1000000): ... if int(i*x) == i: ... print(i) ... break ... 2049 >>> ------------------------------------------------------------------------------- vincent@djoliba:~$ python3 Python 3.4.0 (default, Jun 19 2015, 14:20:21) [GCC 4.8.2] on linux Type "help", "copyright", "credits" or "license" for more information. >>> x = 1 - 1/2**53 >>> assert x == 0.9999999999999999 >>> for i in range(1, 1000000): ... if int(i*x) == i: ... print(i) ... break ... >>> Both on Ubuntu. Vincent -- https://mail.python.org/mailman/listinfo/python-list
