On 29/07/2013 16:43, Steven D'Aprano wrote:
Comparing floats to Fractions gives unexpected results:
# Python 3.3
py> from fractions import Fraction
py> 1/3 == Fraction(1, 3)
False
but:
py> 1/3 == float(Fraction(1, 3))
True
I expected that float-to-Fraction comparisons would convert the Fraction
to a float, but apparently they do the opposite: they convert the float
to a Fraction:
py> Fraction(1/3)
Fraction(6004799503160661, 18014398509481984)
Am I the only one who is surprised by this? Is there a general rule for
which way numeric coercions should go when doing such comparisons?
I'm surprised that Fraction(1/3) != Fraction(1, 3); after all, floats
are approximate anyway, and the float value 1/3 is more likely to be
Fraction(1, 3) than Fraction(6004799503160661, 18014398509481984).
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