class - how to convert a float to a fraction in python? -

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this question has answer here:

i trying define class fraction:

 def __init__(self,num=0,denom=1):         self.num = num         self.denom = denom

and want define add method,

def __add__(self,right):      if type(right) int:         return (self.num/self.denom) + right     if type(right) fraction:         return ((self.num/self.denom)+(right.num/right.denom))   def __radd__(self,left):     return (self.num/self.denom)+left

it works, , returns float. however, want return fraction. example: if test:

f = frac(1,2) f + frac(1,3)  f + 2  frac(1,3) + f 2 + f

i get:

*error: f+frac(1,3) -> 0.8333333333333333 should -> 5/6 *error: f+2 -> 2.5 should -> 5/2 *error: frac(1,3)+f -> 0.8333333333333333 should -> 5/6 *error: 2+f -> 2.5 should -> 5/2

are there methods can convert result float fraction? thank much.

don't create float in first place. example, 

def __add__(self,right):      if type(right) int:         return fraction(self.num + right*self.denom, self.denom)     elif if type(right) fraction:         # reducing answer lowest terms left         # exercise reader         return fraction(self.num*right.denom + right.num*self.denom,                         self.denom*right.denom)

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