Python integer split operator

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Python integer split operator

Asked 5 years ago

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6

Can anyone explain why this function returns -2 and not -1?

print(-3//2)

The operator // does not return the entire part of the division?

1

Welcome George, this link will help you: https://pythonhelp.wordpress.com/2013/06/30/behaviorunexpectedlyin the entire division/

– Luiz Augusto

2019/12/16 at 22:12
1

It is worth noting that the link that Luiz Augusto sent is in python2, so read 3 // 2 when you see 3 / 2 in the article. I did not find an official documentation that explains, but there is a article by Digital Ocean which explains.

– fernandosavio

2019/12/16 at 22:39
Okay, I found something on official documentation on the integer division difference between Python versions 2 and 3.

– fernandosavio

2019/12/16 at 22:40

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by fernandosavio • **9,013** points · Answer 1 · 2019-12-16T22:24:32+00:00

If you check the documentation of numerical types will see that the operator // contains the following description and observation:

x // y: floored quotient of x and y

^{*...The result is Always rounded Towards Minus Infinity...}

Free translation:

x // y: x and y quotient floor

^{*...The result is always rounded to negative infinity...}

As the result of your operation would be -3/2 == -1.5, if you apply to floor function (math.floor in python), or wind it up towards the negative infinity, you will have as a result -2.

You can also check the entrance "Why does -22 // 10 Return -3?" from the Python FAQ to better understand what motivated this decision.