Decimal FTW clear solution for Friendly Number by veky - python coding challenges

Enable Javascript in your browser and then refresh this page, for a much enhanced experience.

Decimal FTW solution in Clear category for Friendly Number by veky

def friendly_number(number, base=1000, decimals=0, suffix='',
                    powers=('',)+tuple('kMGTPEZY')):
    """Format a number as friendly text, using common suffixes."""
    import decimal
    number = decimal.Decimal(number)
    for pw in powers:
        if abs(number) < base: break
        number /= base
    else: number *= base
    val = "{:.{}f}".format(number, decimals) if decimals else str(int(number))
    return val + pw + suffix

March 29, 2014

Comments:

nickie on March 30, 2014, 9:12 p.m.
Why do I have the feeling that if you remove lines 4 and 5 nothing will change? Is this a puzzle after all? :-)

veky on March 30, 2014, 9:46 p.m.
On some machines it won't change, on some (including checkio server that evaluated my solution, feel free to try) it will. That's the beauty of float. :-P This way, I am sure it will work as intended.

shamanu4 on Jan. 22, 2015, 7:51 a.m.
Yeah. We should avoid float calculations everywhere when we want to get predictable results.

veky on Jan. 22, 2015, 9:33 a.m.
Well, I think that's too harsh. float calculations (of continuous functions like `float.add` or `float.truediv`) are usually not the problem, since you're interested in only a few beginning digits. There are many CiO tasks where this is the case. But the comparisons like the one in line 7, or other discontinuous functions like `%`, can fall on the wrong side of the correct answer, and then you have a problem. Decimal is also imperfect, but it's totally predictable since it is written according to a much tighter spec - so when you have the wrong answer, you have it always and everywhere, which makes it much easier to debug. :-)

SandeepManilal on June 13, 2014, 12:26 p.m.
Good stuff! its so clean.

gabor285 on Dec. 17, 2015, 2:28 p.m.
you can delete = import decimal number = decimal.Decimal(number) and replace= (number /= base) to (number = float(number) / base)

veky on Dec. 17, 2015, 9:11 p.m.
Maybe. But are you sure? I mean, are you sure that the second replacement actually does anything? IMO it would matter only with very big and precise integers.

gabor285 on Dec. 17, 2015, 9:30 p.m.
I think the same... only with very big numbers (like= friendly_number(10**32)) and you need solve it too... either with (float, round(x,0),from future import division,or any other....)

gabor285 on Dec. 18, 2015, 12:03 a.m.
I think the same… only with very big numbers (like= friendly_number(10**32)) and you need solve it too… either with (float, round(x,0),from future import division,or the smaller "abs" works too :p )

veky on Dec. 18, 2015, 1:14 p.m.
from future import division?? I think some weird misunderstanding is going on here. You are aware that I'm writing Python 3? :-)

juestr on Sept. 20, 2022, 6:06 p.m.
`decimal` can be used to do quantization, rounding and formatting of the result too. Funnily I didn't use it to find the right power as it can be done with integer math easily.

veky on Sept. 20, 2022, 10:07 p.m.
See the 2nd comment from the top... Integer math is very nice but first you have to get to it.

juestr on Sept. 21, 2022, 12:42 p.m.
My main point was about utilizing `Decimal.quantize` & `.str`, and `decimal.Context.rounding`.

veky on Sept. 21, 2022, 12:56 p.m.
Yes, your solution is very nice. Though I would write that search at the beginning differently. :-) [FWIW, my solution was never meant to showcase Decimal, it's just that the float solution didn't work, so I just applied Decimal as a patch (which you can see from rebinding the `number` name in line 5).]

juestr on Sept. 21, 2022, 1:15 p.m.
The search is a sloppily cleaned up one-liner done in ipython. And I specifically looked for a mission to use Decimal sensibly.

veky on Sept. 21, 2022, 1:35 p.m.
Here is my reordering: <a href="https://py.checkio.org/mission/friendly-number/publications/veky/python-3/juestrs-reordered/">https://py.checkio.org/mission/friendly-number/publications/veky/python-3/juestrs-reordered/</a>

Strings Theory

0 %

PyCharm The Python IDE for Professional Developers. Enjoy productive Python, web and scientific development with PyCharm. Download it now!