Python Fractions
fractions is a module supporting arithmetic with rational numbers.
Usage
Fraction
A Fraction can be instantiated from integers, floats, strings, and Decimal objects.
import fractions
fractions.Fraction(-8, 5) #Fraction(-8, 5)
# The numerator-denominator pair can be given as separate arguments or as a formatted string
fractions.Fraction('-8/5') #Fraction(-8, 5)
# Fraction reduces and moves signs to the numerator automatically
fractions.Fraction(16, -10) #Fraction(-8, 5)
# Note the defaults
fractions.Fraction(123) #Fraction(123, 1)
fractions.Fraction() #Fraction(0, 1)The components can be access with the numerator and denominator properties, or the as_integer_ratio method.
Limit_Denominator
To approximate a fraction, use the limit_denominator method. It takes an integer argument that is used to construct a new Fraction with a denominator no larger than that integer.
import fractions
fractions.Fraction('3.1415926535897932').limit_denominator(1000) #Fraction(355, 113)
See also
Python fractions module documentation
Python Module of the Day article for fractions