Question

I’m new to Python,

After initialising an instance f of class Fraction, I want the method reduce has been invoked, so the print result is after reduced

f = Fraction(3,6)

print f #=> 1/2 not 3/6

here’s the code:

class Fraction(object):
    '''Define a fraction type'''
    def __init__(self, num=0, denom=1):
        '''Create a new Fraction with numerator num and denominator demon'''
        self.numerator = num
        if denom != 0:
            self.denominator = denom
        else:
            raise ZeroDivisionError
    def reduce(self):
        gcd = findgcd(self.numerator, self.denominator)
        self.numerator /= gcd
        self.denominator /= gcd

    def findgcd(self, x, y):
        gcd = None
        min_number = min(x, y)
        for i in range(min_number, 1, -1):
            if x % i == 0 and y % i == 0:
                gcd = i
        return gcd

    def __repr__(self):
        return "{0}/{1}".format(self.numerator, self.denominator)

Answer 1

You have two problems:

1. you need to call self.reduce() in your constructor __init__ to have method reduce() invoked during the instantiation phase.

2. you also need to change:

   def reduce(self):
       gcd = findgcd(self.numerator, self.denominator)
   

   to:

   def reduce(self):
       gcd = self.findgcd(self.numerator, self.denominator)
   

because otherwise your instance will not be able to find findgcd.

---

The following code will fix your problem:

class Fraction(object):
    '''Define a fraction type'''
    def __init__(self, num=0, denom=1):
        '''Create a new Fraction with numerator num and denominator demon'''
        self.numerator = num
        if denom != 0:
            self.denominator = denom
        else:
            raise ZeroDivisionError
        self.reduce()

    def reduce(self):
        gcd = self.findgcd(self.numerator, self.denominator)
        self.numerator /= gcd
        self.denominator /= gcd

    def findgcd(self, x, y):
        gcd = None
        min_number = min(x, y)
        for i in range(min_number, 1, -1):
            if x % i == 0 and y % i == 0:
                gcd = i
        return gcd

    def __repr__(self):
        return "{0}/{1}".format(self.numerator, self.denominator)

>>>> f = Fraction(3,6)
>>>> f
1/2