mantissa and exponent in base 10

[Robert Kern]

On 10/6/10 5:54 PM, Steven D'Aprano wrote:
> I want the mantissa and decimal exponent of a float, in base 10:
>
> mantissa and exponent of 1.2345e7
> =>  (1.2345, 7)
>
> (0.12345, 8) would also be acceptable.
>
>
> The math module has a frexp() function, but it produces a base-2 exponent:
>
>>>> math.frexp(1.2345e7)
> (0.73581933975219727, 24)
>
> Have I missed a built-in or math function somewhere?

|7> def frexp10(x):
..>     exp = int(math.log10(x))
..>     return x / 10**exp, exp
..>

|8> frexp10(1.2345e7)
(1.2344999999999999, 7)

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco