Decimals not equalling themselves (e.g. 0.2 = 0.2000000001)
larry.bates at websafe.com`
Mon Aug 4 00:30:29 CEST 2008
> I am very new to Python (I started learning it just yesterday), but I
> have encountered a problem.
> I want to make a simple script that calculates the n-th root of a given
> number (e.g. 4th root of 625--obviously five, but it's just an example
> :P), and because there is no nth-root function in Python I will do this
> with something like x**(1/n).
> However, with some, but not all, decimals, they do not seem to 'equal
> themselves'. This is probably a bad way of expressing what I mean, so
> I'll give an example:
> >>> 0.5
> >>> 0.25
> >>> 0.125
> >>> 0.2
> >>> 0.33
> As you can see, the last two decimals are very slightly inaccurate.
> However, it appears that when n in 1/n is a power of two, the decimal
> does not get 'thrown off'. How might I make Python recognise 0.2 as 0.2
> and not 0.20000000000000001?
> This discrepancy is very minor, but it makes the whole n-th root
> calculator inaccurate. :\
What are they teaching in computer science classes these days?
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