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IDis31
Asked: 2020-10-30 13:10:45 +0800 CST 2020-10-30 13:10:45 +0800 CST

How can I convert numbers with decimals to fractions in Python?

  • 772

I would like to print numeric values ​​with decimals in their fraction form:

0.5 to 1/2
0.75 to 3/4
4.5 to 9/2

Is there a native library to perform the conversion? How is this conversion done?

python

3 Answers

  1. Best Answer

    You can use the Fractionmodule class fractions:

    >>> from fractions import Fraction
>>> a = Fraction('0.5')
>>> b = Fraction('0.75')
>>> c = Fraction('4.5')
>>> print(a)
1/2
>>> print(b)
3/4
>>> print(c)
9/2

    If you have the numbers saved as reals, then you can make the conversion explicit using str, and then pass that to the Fraction.

    • 8

  2. You can make a recursive function that returns values ​​for the numerator and denominator of the fraction, regardless of whether it is simplified or not. Then you simplify or factor using Euclid's algorithm.

    Here is the code for the algorithm.

    def mcd(a,b):
    assert type(a) == int and type(b) == int and a>0 and b>0
    if a%b != 0:
        return mcd(b,a%b)
    else:
        return b

    Then you do something like numerador=numerador/mcd(numerador,denominador)and denominador=denominador/mcd(numerador,denominador)and print it as a string:

    print(str(numerador)+'/'+str(denominador)).
    • 3

  3. Using the Fractionmodule class fractions, the value of the fraction is not returned when it has infinite decimal numbers, therefore it is necessary to add .limit_denominator()after using the class.

    from fractions import Fraction
a = 2/9
b=Fraction(str(a))
print('Valor de b: ',b)

c=Fraction(str(a)).limit_denominator()
print('Valor de c: ',c)

    And as a result:

    Valor de b:  1111111111111111/5000000000000000
Valor de c:  2/9
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