round() function strange behaviour

[brobbins333 at shaw.ca]

I understand the problem of rounding errors with binary numbers.
However, the rounding functions of other languages  work around it and
return a usable result. What have they got that Python hasn't got?

BR

ps -- your name is very familiar. i think i've read one of your books.

On Sat, 09 Mar 2002 23:13:50 GMT, Erik de Castro Lopo
<nospam at mega-nerd.com> wrote:

>brobbins333 at shaw.ca wrote:
>> 
>> the round() function will sometimes return a predictable result, as
>> in:
>> 
>> round(45.67891, 2)
>> >>> 45.68
>> 
>> but sometimes it will return something like:
>> 
>> round(56.78923, 2)
>> >>> 56.789999999999999
>> 
>> 2.1 and 2.2 both behave this way on two different (Windows) computers.
>> What's going on here?
>
>
>What you will fins is that some numbers like 2, 0.25 etc can be 
>represented exactly in floating point format while others like
>2/3 cannot.
>
>Thats just the way it is.
>
>Erik
>-- 
>+-----------------------------------------------------------+
>  Erik de Castro Lopo  nospam at mega-nerd.com (Yes it's valid)
>+-----------------------------------------------------------+
>BSD:  A psychoactive drug, popular in the 80s, probably developed at UC
>Berkeley or thereabouts.  Similar in many ways to the prescription-only
>medication called "System V", but infinitely more useful. (Or, at least,
>more fun.)  The full chemical name is "Berkeley Standard Distribution".