[Tutor] puzzled by Python 3's print()

[Mark Lawrence]

On 01/07/2010 20:18, Eike Welk wrote:
> Hello Richard!
>
> On Thursday July 1 2010 15:11:21 Richard D. Moores wrote:
>> Thanks to yours and others responses, I've learned some things I
>> didn't know, but remember, I'm starting with long ints such as
>
> Also note that in Python 3 the "/" (division) operator returns a floating
> point number when you divide integers. This is one of the changes that Python
> 3 introduces.
>
> As you are using long integers (and you were previously writing about prime
> numbers) the precision of floating point numbers might not be enough for your
> purposes.
>
> Therefore you should probably use the integer division operator: "//"
>
>
> The following (edited) snippet from IPython demonstrates "//" and the loss of
> precision when using "/":
>
>
> ...
> Python 2.6.2 (r262:71600, Mar 29 2010, 15:30:01)
> Type "copyright", "credits" or "license" for more information.
>
> IPython 0.10 -- An enhanced Interactive Python.
> ...
>
> In [1]: from __future__ import  division
>
> In [2]: a = 1000000000000000000000000000000000000000000000000000000002
>
> In [3]: a
> Out[3]: 1000000000000000000000000000000000000000000000000000000002L
>
> In [4]: a//2
> Out[4]: 500000000000000000000000000000000000000000000000000000001L
>
> In [5]: a/2
> Out[5]: 4.9999999999999994e+56
>
> In [6]: long(a/2)
> Out[6]: 499999999999999937061060126016582882140297920412594995200L
>
>
> Eike.
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Drat, drat and double drat, I believe Dick Dastardly from the Wacky 
Races cartoons.  I meant to mention this, got side-tracked and 
completely forgot, sorry.

Kindest regards.

Mark Lawrence.