On 19 September 2012 19:27, Andrew Tritt <ajtr...@lbl.gov> wrote: > Hello, > > I am new to python, and I was experimenting with the round function, and > came across what appears to be a bug in floating point rounding. I am > guessing there is a valid explanation for it. > > When I round the floating points 10.6[0-9]5 to two decimal places, it > rounds as expected for 6 of the 10, but not for the other 4. When I try the > same for 10.7[0-9]5, I experience the same problem, but for 5 of the 10 > possibilties, and not for the analogous floats. > > Also, python storing the numbers as they are represented at the prompt. > i.e. 10.665 is stored as 10.665, not something like 10.665000001 or > 10.66499999999. > > Can anyone explain to me what's happening? >
It is because Python (like all programming languages I know) represents floating point numbers in base 2. This is discussed in the python.orgtutorial: http://docs.python.org/tutorial/floatingpoint.html Oscar
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