round() to nearest .05 ?

Kent Johnson kent3737 at yahoo.com
Mon Nov 15 22:46:04 CET 2004


tertius wrote:
> Hi,
> 
> I'm trying to round my float total to the nearest .05 cents.

If you want the *nearest* .05, this works:
 >>> def fivecents(f):
...   return round(f*2.0, 1) / 2.0
...
 >>> for f in [ 12.01, 0.14, 2.28, 703.81]:
...   print f, fivecents(f)
...
12.01 12.0
0.14 0.15
2.28 2.3
703.81 703.8

> 12.01    should produce 12.00
>  0.14    should produce 0.10
>  2.28          "        2.25
> 703.81         "        703.80

Your example seems to be rounding down always, not what I would call 
nearest. Here is one that always rounds toward zero:
 >>> def lowerfivecents(f):
...   return int(f*20) / 20.0
...
 >>> for f in [ 12.01, 0.14, 2.28, 703.81]:
...   print f, lowerfivecents(f)
...
12.01 12.0
0.14 0.1
2.28 2.25
703.81 703.8

If you want to always round toward more negative, use math.floor() 
instead of int().

Kent
> 
> "%.02f"%100.0099 produces 100.01 (which I know is right)
> No combination of round and/or "%.02f" works for me.
> 
> What's the best way to get there? Should I write a function to manage my 
> rounding or is there a simpler/better way?
> 
> TIA
> T



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