How can modulo deal with big float numbers

Question

Hey i'm trying to use modulo with big float numbers but python don't seems to like those big numbers. My goal is to check if the division of 2 integers give me an integer or not (so if division_result%1 == 0 or not)

Example:

x = 3**2
x = x+0.3
x%1

result = 0.3000000000000007 | expected = 0.3

x = 3**199
x = x+0.3
x%1

result = 0.0 |expected = 0.3

How can I improve the precision of the result / or find a clever way to check if the division give me an integer?

Answer 1

not all fractions can be represented exactly as floats. your approach will therefore not work (as expected).

what you might try is the fractions module:

from fractions import Fraction

print(repr(Fraction(25, 5)))  # Fraction(5, 1)

this a way you could use Fraction:

def div_result_int(a, b):

    f = Fraction(a, b)
    return f.denominator == 1

print(div_result_int(a=25, b=5))  # True
print(div_result_int(a=25, b=3))  # False

Answer 2

For integers x and y, the fraction y/x is an integer if and only if y % x == 0. As long as x and y are integers, you don't have to worry about floating point errors or special numerical classes or anything. Just make sure that x and y are actually represented as integers and not floats. And since python can handle large integers, this works for integers longer than 64 bits, e.g:

> x = 17**100
> y = 17**200    
> y % x
0
> (y + 1) % x
1