[issue41071] from an int to a float , why
mike stern added the comment: i am calm but sometimes I am wondering if the philosophy behind python is really like they claimed to make it very simple. Well I see a lot of confusions sometimes , and this is one From: report=bugs.python@roundup.psfhosted.org on behalf of Tim Peters Sent: Monday, June 22, 2020 5:59 PM To: rskir...@hotmail.com Subject: [issue41071] from an int to a float , why Tim Peters added the comment: Mike, read that exchange again. You originally wrote "print(2 / 2) gives 2.0 instead of 2" but you didn't _mean_ that. You meant to say it "gives 1.0 instead of 1", or you meant something other than "2 / 2"). In Python 3, >>> print(2 / 2) 1.0 Which is what Serhiy said it does. For the rest, read the PEP again after you calm down. In particular, "Classic division will remain the default in the Python 2.x series; true division will be standard in Python 3.0." Also all true. -- ___ Python tracker <https://bugs.python.org/issue41071> ___ -- ___ Python tracker <https://bugs.python.org/issue41071> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41071] from an int to a float , why
mike stern added the comment: sorry but that article was about version 2.2 in 2000 Created:11-Mar-2001 Python-Version: 2.2 where is the one for 3.7 From: report=bugs.python@roundup.psfhosted.org on behalf of Tim Peters Sent: Monday, June 22, 2020 5:20 PM To: rskir...@hotmail.com Subject: [issue41071] from an int to a float , why Tim Peters added the comment: Read the PEP Serhiy already linked to: https://www.python.org/dev/peps/pep-0238/ This was a deliberate change to how "integer / integer" works, introduced with Python 3. -- nosy: +tim.peters status: open -> closed ___ Python tracker <https://bugs.python.org/issue41071> ___ -- ___ Python tracker <https://bugs.python.org/issue41071> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41071] from an int to a float , why
mike stern added the comment: I appreciate your answer I just didn't like how she answered earlier saying I cannot reproduce. 2 / 2 gives 1.0 to me. which is not true thanks anyway, now i am gonna have to do some reading From: report=bugs.python@roundup.psfhosted.org on behalf of Tim Peters Sent: Monday, June 22, 2020 5:20 PM To: rskir...@hotmail.com Subject: [issue41071] from an int to a float , why Tim Peters added the comment: Read the PEP Serhiy already linked to: https://www.python.org/dev/peps/pep-0238/ This was a deliberate change to how "integer / integer" works, introduced with Python 3. -- nosy: +tim.peters status: open -> closed ___ Python tracker <https://bugs.python.org/issue41071> ___ -- ___ Python tracker <https://bugs.python.org/issue41071> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41071] from an int to a float , why
mike stern added the comment: Not satisfied with that reply you can't just decide to close the ticket without even giving a reasonable answer, or even try that on 2.7 or 3.7 to see if it is true what I said. Besides, that is not a convincing answer, that is actually no answer at all!!! I made my research and this is what is it https://stackoverflow.com/questions/183853/what-is-the-difference-between-and-when-used-for-division in python 2.7 print((20 / 3)) > 6 but print((20.0 / 3)) or print((20 / 3.0)) or print((20.0 / 3.0)) > 6.667 however print((20 / 2)) > 10 # integer number in python 3.7 print((20 / 3)) > 6.667 not only that but even print((20 / 2)) > 10.0 # float number unless you use // print((20 // 2)) > 10 can someone really explain this ? -- status: closed -> open ___ Python tracker <https://bugs.python.org/issue41071> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41071] from an int to a float , why
New submission from mike stern : please I would like to know why python changes an integer result in a division to a float even in the result is even like print(2 / 2) gives 2.0 instead of 2 or a = 2 / 2 print(a) -- components: Interpreter Core messages: 372033 nosy: rskir...@hotmail.com priority: normal severity: normal status: open title: from an int to a float , why type: behavior versions: Python 3.7 ___ Python tracker <https://bugs.python.org/issue41071> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
mike stern added the comment: sorry but I don't see the option to delete From: report=bugs.python@roundup.psfhosted.org on behalf of Terry J. Reedy Sent: Monday, June 15, 2020 11:46 AM To: rskir...@hotmail.com Subject: [issue40981] increment is wrong in 3.7 but not in 2.7 Terry J. Reedy added the comment: Mike, when you respond by email, delete the text you are responding to. Your email is posted below the already posted text and the quote is useless noise that makes it harder to see what you wrote. Newcomers to Python who think they have seen a bug should best post to python-list or similar forums asking "Is this a bug? If not, please explain.". -- nosy: +terry.reedy ___ Python tracker <https://bugs.python.org/issue40981> ___ -- ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
mike stern added the comment: I appreciate taking the time to explain , I just wished the other guys did that instead of just closing the ticket on my face. I wished at least they suggested me to use round() without any aggravations but thanks anyway From: report=bugs.python@roundup.psfhosted.org on behalf of Steven D'Aprano Sent: Monday, June 15, 2020 2:51 AM To: rskir...@hotmail.com Subject: [issue40981] increment is wrong in 3.7 but not in 2.7 Steven D'Aprano added the comment: > I wouldn't trust a language behaving crazy like this I guess then you won't trust C, Java, C++, Swift, Javascript, Ruby, Cobol, Fortran, and pretty much every programming language in existence. The only ones that escape this are ones that don't have floating point numbers at all. > you haven't tried it on 2.7 did you ? We know how Python 2.7 works. Some of us have been using Python for 25 years, since version 1.5 or older. Do you think you are the first person to have noticed this? There are hundreds of thousands of Python programmers, believe me you're not the first, or even the ten-thousandth person to have noticed. Python 2.7 rounds off the default display of floats to make them look "pretty" instead of displaying their actual value. Try this in 2.7 and see what happens: i=0 while i < 1.2: i += 0.1 print "default:", i, "actual: %.24f" % i The calculations are *precisely* the same, only the display is different. Honestly Mike, this is not a Python issue, it is universal to all languages with fixed-size floating point numbers. This is not a bug, it is how numeric computing works *everywhere*. People write peer reviewed scientific papers about this: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.22.6768 https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html If you want to educate yourself on the issue, rather than just rant about not trusting the language and abuse people who have been using the language for decades, you could do a lot worse than to start here: https://randomascii.wordpress.com/2012/05/20/thats-not-normalthe-performance-of-odd-floats/ https://randomascii.wordpress.com/2012/04/05/floating-point-complexities/ and take careful note that the author talks about C, probably the most common, fundamental and trusted programming language in the world. (Also remember that when Bruce Dawson talks about floats in C, they are half the precision of Python floats, which are C doubles.) The bottom line is that floats are not the infinitely precise exact mathematical numbers we learn about in school, they are more like the numbers you get on a calculator. -- nosy: +steven.daprano ___ Python tracker <https://bugs.python.org/issue40981> ___ -- ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
mike stern added the comment: you can at least try it and see for yourself that what I am saying is actually true but never mind I will keep on opening tickets until someone tries it on 2.7 and see what I am talking about From: Redwane Freedom Is-to-Be-With-God Sent: Monday, June 15, 2020 2:45 AM To: Python tracker Subject: Re: [issue40981] increment is wrong in 3.7 but not in 2.7 what is rude is to talk to me in an autoritative way like you do you haven't even checked what I said , I said it working in Python 2.7 and it is not in 3.7 and you want to just read me an article. From: report=bugs.python@roundup.psfhosted.org on behalf of Christian Heimes Sent: Monday, June 15, 2020 2:40 AM To: rskir...@hotmail.com Subject: [issue40981] increment is wrong in 3.7 but not in 2.7 Christian Heimes added the comment: Python's float are IEE 754 floats for over 25 years and since Python 1.x, maybe earlier. IIRC standard is from 1985. It's how CPUs have dealt with floats for over 35 years. By the way it's is incredible rude to keep re-opening a bug and responding on a closed bug. Do not reopen the bug again. -- status: open -> closed ___ Python tracker <https://bugs.python.org/issue40981> ___ -- ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
mike stern added the comment: you can at least try it and see for yourself that what I am saying is actually true but never mind I will keep on opening tickets until someone tries it on 2.7 and see what I am talking about From: Redwane Freedom Is-to-Be-With-God Sent: Monday, June 15, 2020 2:45 AM To: Python tracker Subject: Re: [issue40981] increment is wrong in 3.7 but not in 2.7 what is rude is to talk to me in an autoritative way like you do you haven't even checked what I said , I said it working in Python 2.7 and it is not in 3.7 and you want to just read me an article. From: report=bugs.python@roundup.psfhosted.org on behalf of Christian Heimes Sent: Monday, June 15, 2020 2:40 AM To: rskir...@hotmail.com Subject: [issue40981] increment is wrong in 3.7 but not in 2.7 Christian Heimes added the comment: Python's float are IEE 754 floats for over 25 years and since Python 1.x, maybe earlier. IIRC standard is from 1985. It's how CPUs have dealt with floats for over 35 years. By the way it's is incredible rude to keep re-opening a bug and responding on a closed bug. Do not reopen the bug again. -- status: open -> closed ___ Python tracker <https://bugs.python.org/issue40981> ___ -- ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
mike stern added the comment: what is rude is to talk to me in an autoritative way like you do you haven't even checked what I said , I said it working in Python 2.7 and it is not in 3.7 and you want to just read me an article. From: report=bugs.python@roundup.psfhosted.org on behalf of Christian Heimes Sent: Monday, June 15, 2020 2:40 AM To: rskir...@hotmail.com Subject: [issue40981] increment is wrong in 3.7 but not in 2.7 Christian Heimes added the comment: Python's float are IEE 754 floats for over 25 years and since Python 1.x, maybe earlier. IIRC standard is from 1985. It's how CPUs have dealt with floats for over 35 years. By the way it's is incredible rude to keep re-opening a bug and responding on a closed bug. Do not reopen the bug again. -- status: open -> closed ___ Python tracker <https://bugs.python.org/issue40981> ___ -- ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
mike stern added the comment: Christian Heimes you haven't tried it on 2.7 did you ? -- status: closed -> open ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7
mike stern added the comment: Christian Heimes why did you close it -- status: closed -> open ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7 but not in 2.7
Change by mike stern : -- nosy: -serhiy.storchaka, terry.reedy title: increment is wrong in 3.7 -> increment is wrong in 3.7 but not in 2.7 ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7
mike stern added the comment: so anybody can close a ticket ? anybody can say their point of view and close a ticket, is that how it goes? this is not serious who is managing this ? is this how we can trust a programming language? it sounds like we are dealing with irresponsible kids here please don't close this ticket until we understand that there is actually this problem in 3.7 and that the problem is fixed -- nosy: -SilentGhost status: closed -> open ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7
mike stern added the comment: problem actually more serious, it is here print(0.7+0.1) , which gives .7999 same thing when adding the .1 increment to 4.8 , 5.1 etc ... I am not sure of the pattern but it is acting up with some numbers who will fix this , this is serious I wouldn't trust a language behaving crazy like this the problem is not there in 2.7 why you closed the ticket , who are you -- status: closed -> open ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue40981] increment is wrong in 3.7
New submission from mike stern : I noticed i big problem making a simple increment of .1 in python 3.7 using while the result is wrong i=0 while i < 1.2: i += 0.1 print(i) result == RESTART: C:/Users/icosf/AppData/Local/Programs/Python/Python37-32/bb.py == 0.1 0.2 0.30004 0.4 0.5 0.6 0.7 0.7999 0.8999 0. 1.0999 1.2 what the heck is going on, can someone explain to me -- assignee: terry.reedy components: IDLE messages: 371519 nosy: rskir...@hotmail.com, terry.reedy priority: normal severity: normal status: open title: increment is wrong in 3.7 type: behavior versions: Python 3.7 ___ Python tracker <https://bugs.python.org/issue40981> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
