On Tue, Nov 30, 2010 at 13:23, Steven D'Aprano <st...@pearwood.info> wrote: > Richard D. Moores wrote: >> >> Please take a look at 2 functions I just wrote to calculate the >> harmonic and geometric means of lists of positive numbers: >> <http://tutoree7.pastebin.com/VhUnZcma>. >> >> Both Hlist and Glist must contain only positive numbers, so I really >> need to test for this inside each function. But is there a good way to >> do this? What should the functions return should a non-positive number >> be detected? Is there a conventional Pythonic way to do this? >
> (2) If you don't trust that a sensible exception will be raised, then do > your own error checking, and raise an exception. I'll go with this one because I do want both Hlist and Glist to contain only positive real numbers. So I'll go with Jerry Hill's suggestion for both H and G. See the two revised functions at <http://tutoree7.pastebin.com/VfYLpFQq>. > For what it's worth, I have a module of statistics functions (shameless > plug: http://pypi.python.org/pypi/stats and > http://code.google.com/p/pycalcstats -- feedback and bug reports welcome) An impressive collection. Thanks for sharing! > that includes the harmonic and geometric mean. My harmonic mean looks like > this: > > def harmonic_mean(data): > try: > m = mean(1.0/x for x in data) > except ZeroDivisionError: > return 0.0 > if m == 0.0: > return math.copysign(float('inf'), m) > return 1/m math.copysign! Didn't know about that one. But "mean"? It's not a built-in function.. Dick > Notice that if the data includes one or more zeroes, the harmonic mean > itself will be zero: limit as x->0 of 1/x -> infinity, and 1/infinity -> 0. > If the sum of reciprocals itself cancels to zero, I return the infinity with > the appropriate sign. The only exceptions that could occur are: > > * mean will raise ValueError if the data is empty; > * if an argument is non-numeric, TypeError will occur when I take the > reciprocal of it. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
