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pythonfractions

Can I get a fraction from a number in python?

I am doing some calculations and before outputting I want to change the number to a fraction. For example 0.25 would become 1/4, well in a list of the two numbers [1, 4].

Solution

  • Use the fractions module to do that:

    >>> import fractions
>>> fractions.Fraction(0.25)
Fraction(1, 4)
>>> f = fractions.Fraction(0.25)
>>> f.numerator
1
>>> f.denominator
4

    For arbitrary floats as input, you really want to use the .limit_denominator() method to limit your fractions to sane approximations of the floating point number:

    >>> from math import pi, cos
>>> fractions.Fraction(cos(pi/3))
Fraction(4503599627370497, 9007199254740992)
>>> fractions.Fraction(cos(pi/3)).limit_denominator()
Fraction(1, 2)