I saw a twitter post pointing out that -12/10 = -2 in Python. What causes this? I thought the answer should (mathematically) be one. Why does python "literally" round down like this?
>>> -12/10
-2
>>> 12/10
1
>>> -1*12/10
-2
>>> 12/10 * -1
-1
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paxdiablo
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kilojoules
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This may be helpful: [In Python, what is a good way to round towards zero in integer division?](http://stackoverflow.com/questions/19919387/in-python-what-is-a-good-way-to-round-towards-zero-in-integer-division) – awesoon Aug 17 '15 at 04:16
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4http://stackoverflow.com/questions/5535206/python-negative-integer-division-surprising-result Does answer given here help? – Vineet Kumar Doshi Aug 17 '15 at 04:16
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do like this -12/float(10) – open source guy Aug 17 '15 at 04:18
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1Are you asking why the result isn't `1.2`, or why the result isn't `-1`? – Yu Hao Aug 17 '15 at 04:19
2 Answers
5
This is due to int rounding down divisions. (aka Floor division)
>>> -12/10
-2
>>> -12.0/10
-1.2
>>> 12/10
1
>>> 12.0/10
1.2
f.rodrigues
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4
This is known as floor division (aka int division). In Python 2, this is the default behavior for -12/10. In Python 3, the default behavior is to use floating point division. To enable this behavior in Python 2, use the following import statement:
from __future__ import division
To use floor division in Python 3 or Python 2 with this module imported, use //.
More information can be found in the Python documentation, "PEP 238: Changing the Division Operato".
J. Doe
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