CODEWITHSUNDEEP
pythonfractions
Rekcah
Rekcah

Reputation: 35

Fraction function from fractions module python problem

>>> n=F.Fraction(3.56)
>>> n
Fraction(8016407336719483, 2251799813685248)
>>> n=F.Fraction('3.56')
>>> n
Fraction(89, 25)

Is it working as intended? Both results are correct, but the first one seems to be over the top. I stubmled it upon while solving this kata from codewars.

Upvotes: 3

Views: 439

Answers (2)

Erick Kokubum
Erick Kokubum

Reputation: 56

Because of the usual issues with binary floating-point, the Fraction(floating) doesn't return the expected fraction object, different from the decimal or string, that is treated like a exact number.

But you can treat this issue using a method called "limit_denominator" that have a default argument "max_denominator=1000000",so, you only need to call:

Fraction(3.16).limit_denominator()

Take a look at the docs: https://docs.python.org/3/library/fractions.html#fractions.Fraction.limit_denominator

Upvotes: 3

Lab
Lab

Reputation: 226

When you wrote 3.56, it means you declared a number 3.56 as float type. And float type has a small deviation, which cause there's also a small deviation when it converts to fraction type.

But when you wrote '3.56', you declared a string. String has a limited length, thus there's no more deviation. When you convert it to string, they will convert it to the exact value.

See also: https://www.daniweb.com/programming/threads/506664/mod-unexpected-result

Upvotes: 1

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