如何在实例的初始化过程中调用某些方法在Python

Question

我是新来的Python，

初始化Fraction类的一个实例f后，我想reduce已调用的方法，所以print结果降低

f = Fraction(3,6) 

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

这里后的代码：

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

你有两个问题：

1. 你需要调用self.reduce()在构造函数__init__有在实例化阶段调用的方法reduce()。

2. ，你也需要改变：

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

   到：

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

，否则您的实例将无法找到findgcd。

---

下面的代码将解决您的问题：

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 

Answer 2

什么阻止你调用self.reduce()在__init__方法结束？