python析構(gòu)函數(shù)用法及注意事項(xiàng)

class Animal:
    def __del__(self):
        print("銷毀對(duì)象{0}".format(self))
cat = Animal()
cat2 = Animal()
del cat2
print("程序結(jié)束")

class Animal:
    def __del__(self):
        print("調(diào)用父類 __del__() 方法")
        
class Bird(Animal):
    def __del__(self):
       # super(Bird,self).__del__()  #方法1：顯示調(diào)用父類的del方法
        print("調(diào)用子類 __del__() 方法")
 
cat = Bird()
#del cat   #只能調(diào)用子類里面的__del__
#super(Bird,cat).__del__() #方法2：顯示調(diào)用父類的__del__

#coding=utf-8
'''
魔法方法，被__雙下劃線所包圍
在適當(dāng)?shù)臅r(shí)候自動(dòng)被調(diào)用
'''
#構(gòu)造init、析構(gòu)del
class Rectangle:
  def __init__(self,x,y):
    self.x = x
    self.y = y
    print('構(gòu)造')
  '''
  del析構(gòu)函數(shù)，并不是在del a對(duì)象的時(shí)候就會(huì)調(diào)用該析構(gòu)函數(shù)
  只有當(dāng)該對(duì)象的引用計(jì)數(shù)為0時(shí)才會(huì)調(diào)用析構(gòu)函數(shù)，回收資源
  析構(gòu)函數(shù)被python的垃圾回收器銷毀的時(shí)候調(diào)用。當(dāng)某一個(gè)對(duì)象沒有被引用時(shí)，垃圾回收器自動(dòng)回收資源，調(diào)用析構(gòu)函數(shù)
  '''
  def __del__(self):
    print('析構(gòu)')
  def getPeri(self):
    return (self.x + self.y)*2
  def getArea(self):
    return self.x * self.y
if __name__ == '__main__':
  rect = Rectangle(3,4)
  # a = rect.getArea()
  # b = rect.getPeri()
  # print(a,b)
  rect1 = rect
  del rect1
  # del rect
  while 1:
    pass