Why Python 3?

[Gregory Ewing]

Terry Reedy wrote:
> On 4/19/2014 9:06 PM, Gregory Ewing wrote:
> 
>> Similarly, when you write // you're explicitly requesting
>> integer division.
> 
> One is requesting 'floor division'
> 
>  >>> 3.0//2.0
> 1.0

In general that's true, but I'm talking about a context
in which you have some expectations as to the types of the
operands.

Most of the time, there are two possible scenarios:

1) The algorithm operates on integers, and the contract is
that you only get passed ints. In that case, you use //
and know that the result will be an int.

2) The algorithm operates on non-integers, and the contract
is that you get passed either ints or floats, with ints being
understood as standing in for floats. In that case, you
use / and know that it will perform float division and
return a float.

If someone passes you a float in case (1) it's true that
// won't return an int, but then they've violated the
contract.

-- 
Greg