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GitHub Repository: jackfrued/Python-100-Days
 Path: blob/master/Day01-15/code/Day09/rational.py
Views: 729
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"""

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运算符重载 - 自定义分数类

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Version: 0.1

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Author: 骆昊

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Date: 2018-03-12

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"""

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from math import gcd

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class Rational(object):

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    def __init__(self, num, den=1):

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        if den == 0:

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            raise ValueError('分母不能为0')

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        self._num = num

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        self._den = den

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        self.normalize()

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    def simplify(self):

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        x = abs(self._num)

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        y = abs(self._den)

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        factor = gcd(x, y)

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        if factor > 1:

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            self._num //= factor

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            self._den //= factor

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        return self

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    def normalize(self):

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        if self._den < 0:

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            self._den = -self._den

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            self._num = -self._num

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        return self

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    def __add__(self, other):

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        new_num = self._num * other._den + other._num * self._den

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        new_den = self._den * other._den

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        return Rational(new_num, new_den).simplify().normalize()

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    def __sub__(self, other):

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        new_num = self._num * other._den - other._num * self._den

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        new_den = self._den * other._den

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        return Rational(new_num, new_den).simplify().normalize()

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    def __mul__(self, other):

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        new_num = self._num * other._num

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        new_den = self._den * other._den

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        return Rational(new_num, new_den).simplify().normalize()

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    def __truediv__(self, other):

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        new_num = self._num * other._den

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        new_den = self._den * other._num

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        return Rational(new_num, new_den).simplify().normalize()

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    def __str__(self):

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        if self._num == 0:

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            return '0'

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        elif self._den == 1:

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            return str(self._num)

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        else:

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            return '(%d/%d)' % (self._num, self._den)

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if __name__ == '__main__':

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    r1 = Rational(2, 3)

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    print(r1)

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    r2 = Rational(6, -8)

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    print(r2)

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    print(r2.simplify())

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    print('%s + %s = %s' % (r1, r2, r1 + r2))

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    print('%s - %s = %s' % (r1, r2, r1 - r2))

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    print('%s * %s = %s' % (r1, r2, r1 * r2))

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    print('%s / %s = %s' % (r1, r2, r1 / r2))

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