Arithmetics is broken in Python?

Question

When I do this calculation 2*(5+5/(3+3))*3 I get 30 in Python (2.7). But what it seems is that 2*(5+5/(3+3))*3is equal to 35. Can someone tell me why python gives me the answer of 30 instead of 35? I've tested with JavaScript, Lua and Mac Calculator and they show me 35.

Why does Python calculate wrong?

http://ideone.com/yiFJxS

That's because `5/6` yields 0 in python 2 and everyone else evaluate it as a decimal output — Kamehameha, Apr 28 '16 at 11:27
@DanielRoseman: so what got fixed in Python 3? `/` forces its arguments into floats? — Jongware, Apr 28 '16 at 11:28
No, but the *result* of dividing two integers in Python 3 is always a float. See https://docs.python.org/2/howto/pyporting.html#division — Daniel Roseman, Apr 28 '16 at 11:31
Okey, thank you. All I need is to change integers to float on division. Tnx. — LUCAS, Apr 28 '16 at 11:31
`2*(5+5/float(3+3))*3` works. `5+5/(3+3)` is rounded down or seen as `int()`, it seems — jDo, Apr 28 '16 at 11:31
Yes, Python 3 seems to assume its a float, Python 2 gives you an integer. 2*(5+5./(3+3))*3 results in 35.0. So it's probably best to check for possible integer division yourself and use floats there. — Frederic Klein, Apr 28 '16 at 11:32
The Python 0, 1 and 2 division was deemed broken a long time ago. It has now been fixed in Python 3. Please switch to Python 3, which is the sanest solution, or otherwise use `from __future__ import division` — Antti Haapala -- Слава Україні, Apr 28 '16 at 12:40
@DanielRoseman / is not always an integer division in Python 2. `//` OTOH always is a flooring division in both Python 2 and 3. — Antti Haapala -- Слава Україні, Apr 28 '16 at 12:41

score 6 · Accepted Answer · answered Apr 28 '16 at 11:27

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This happens because of the piece 5/(3 + 3) which evalautes to 0. You need to use either of them as float.

answered Apr 28 '16 at 11:27

Anshu Kumar

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MildCorma · Answer 2 · 2016-04-28T11:32:48.737

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Always assume it's an issue with something you're doing rather than with an entire coding language!

It works fine for me in Python shell. 35 is the expected answer and 35 is what we get! Most likely something on your end or a mis-type / you've miss-commented something out. This is from copy pasting your code above.

edit: Who is more likely to be wrong, an individual? Or the masses? Occams razor. In this case I assumed he was using 3 and not 2.7 which led to the correct assumption as it does work in 3.

edited Apr 28 '16 at 11:32

answered Apr 28 '16 at 11:27

MildCorma

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If you always assume there's an issue with yourself, you'll never find bugs in the language. – erip Apr 28 '16 at 11:29

Arithmetics is broken in Python?

2 Answers2