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Python 3, an illustrated tour Transcripts

Chapter: Numbers

Lecture: Division

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In this video we're going to talk about integer division.

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This came out in Python 3 pep 238 introduced it.

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In Python 2 when you divided a number by another number

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if you divided floats, you'd get back a float as a result,

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but for integers, you would get back an integer as a result.

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And this is called floor division.

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Guido writes in his Python history blog about how this was a mistake

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and Python 3 attempted to rectify this

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by changing the behavior of the division operator.

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So in Python 3 slash does what's called true division

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there's a __truediv__

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and double slash does floor division __floordiv__

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So if I divide 2 by 3 in Python 3, I get point .6666,

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and if I say 2//3 then I get that floor division and I get back 0 as a result.

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Note that floor division also works on floats

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if I say 2.0 divided by 3.1, I get .66,

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but if I do floor division on those numbers, I get 0.0

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and because everything is an object in Python,

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if we want to we can go through the steps

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to show that you can invoke __truediv__ on an integer and __floordiv__ as well.

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Now again, you typically don't do this, we typically don't call the dunder methods

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but they're there because in Python everything is an object

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and you can call the object methods if you want to.

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Quick summary, in Python 3 when you divide two numbers,

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you will get a float as a result.

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If you don't want a float then use a double divide

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to do what's called floor division.