At Wednesday 13/12/2006 03:14, Simon Schuster wrote:
gc = float(count(cds, 'g') + count(cds, 'c'))/ len(cds)
which should yield: 0.54460093896713613..
but when I ran it I got: 0.544600938967
looking now I see it's truncating after a certain number of decimal
places. any ideas why?
Floating point numbers have finite precision so at *some* point the
digits have to stop. The print statement uses str() to convert its
arguments, and for a Python float that uses 12 digits. You could use
repr() instead and get 17 digits:
>>> print repr(gc)
0.54460093896713613
Read the Appendix B in the Python Tutorial for more info. Or look for
"David Goldberg. What every computer scientist should know about
floating-point arithmetic. ACM Computing Surveys, 23(1):5--48, March 1991."
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Gabriel Genellina
Softlab SRL
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