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Comparing float to Fraction in python [CLOSED]

+1 vote
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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?

closed with the note: None
posted Jul 29, 2013 by Deepankar Dubey

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1 Answer

+1 vote
 
Best answer

Any float can be precisely represented as a Fraction. Not so in the other direction. So from that standpoint it makes sense to me to cast to Fraction when comparing.

answer Jul 29, 2013 by Sonu Jindal
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