python类分数 [英] python class fraction numbers

问题描述

我编写了一个代码，使用户可以以 d / n的形式输入两个分数。

I made a code that makes the user input two fraction numbers in the form "d/n".

如何使其打印出简化的形式？分数？

How can I make it print the reduced form of the fraction ?

例如：当我键入2/4时，它会显示1/2？

ex: when I type 2/4 it prints 1/2?

   import sys

class Rational:

  def __init__(self,n,d):
    self.numerator= n
    self.denominator= d
  def value(self):
    return float(self.numerator)/float(self.denominator)

  def __repr__(self):
    return "%d/%d ~ %g" % (self.numerator,self.denominator,self.value())
  def read(self):
    while 1:
      try:
        s=raw_input("Enter fraction n/d: ")
        n,d= s.split("/")
        self.numerator= int(n)
        self.denominator= int(d)
      except KeyboardInterrupt:
        print
        exit()
      except:
        print sys.exc_info()[0]
        print "bad input, try again."
      else:
        if int(d)==0:
          print "The denominator cannot be zero. Try again."
        elif int(d)<0:
          print "The denominator cannot be negative. Try again."
        else:
          return

r1=Rational(1,1)
r1.read()
print r1

r2=Rational(1,1)
r2.read()
print r2

推荐答案

使用 fractions.Fraction（）类，并让它为您完成工作：

Use the fractions.Fraction() class and have it do the work for you:

>>> import fractions
>>> fractions.Fraction(2, 4)
Fraction(1, 2)

简化分数您自己，计算最大公约数：

To simplify fractions yourself, calculate the greatest common divisor:

def gcd(a, b):
    while b:
        a, b = b, a%b
    return a

g = gcd(numerator, denominator)
numerator //= g
denominator //= g

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