[Tutor] Integer division (Was: Re: Format strings for variables - how?)

[Kalle Svensson]

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Sez David Porter:
> * Viktor Lakics <lakicsv@usa.net>:
> > a=3D1
> > b=3D3
> > print "%0.2f" %(a/b)
> >=20
> > The above code gives me 0.00 as a result, while I wanted to get
> > 0.33...
>=20
> The reason is that the numbers you are dividing are not floats. Because of
> that, you are doing integer division.
>=20
> >>> a =3D 1.0
> >>> b =3D 3
> print "%0.2f" %(a/b)
>=20
> gives 0.33. You must add a decimal point to one (or more) of the numbers.

Now, you might (should, I think) wonder:  Why?
Basically, I think there are two reasons python has integer division.

 1) C has truncating integer division.  Python is implemented in C.  Some of
the initial target users for Python were C programmers.

 2) There is no way to handle division of two integers that everybody likes.
Some want truncating integer division (chopping off the remainder), some wa=
nt
conversion to float (which loses exact representation), some want rational
math (resource intensive), some want the Spanish Inquisition...

 3) It would break a lot of existing code if it was changed tomorrow.
=20
Three reasons.

The way it works today is perhaps not the most obvious for a newcomer to
programming or one with experience in languages using different solutions,
but when you get used to it, it's at least as good as any of the
alternatives, IMHO.

HTH,
  Kalle
--=20
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