How to use __del__ method in pyatom

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ClassDel.py

Source:ClassDel.py Github

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1# Python __del__方法：销毁对象2#3# 与 __init__() 方法对应的是 __del__() 方法，__init__() 方法用于初始化 Python 对象，而 __del__() 则用于销毁 Python 对象，即在任何 Python 对4# 象将要被系统回收之时，系统都会自动调用该对象的 __del__() 方法。5#6# 当程序不再需要一个 Python 对象时，系统必须把该对象所占用的内存空间释放出来，这个过程被称为垃圾回收（GC，Garbage Collector），Python 会自动回收7# 所有对象所占用的内存空间，因此开发者无须关心对象垃圾回收的过程。8#9# Python 采用自动引用计数（ARC）方式来回收对象所占用的空间，当程序中有一个变量引用该 Python 对象时，Python 会自动保证该对象引用计数为 1；当程序中10# 有两个变量引用该 Python 对象时，Python 会自动保证该对象引用计数为 2，依此类推，如果一个对象的引用计数变成了 0，则说明程序中不再有变量引用该对象，11# 表明程序不再需要该对象，因此 Python 就会回收该对象。12#13# 大部分时候，Python 的 ARC 都能准确、高效地回收系统中的每个对象。但如果系统中出现循环引用的情况，比如对象 a 持有一个实例变量引用对象 b，而对象 b 又14# 持有一个实例变量引用对象 a，此时两个对象的引用计数都是 1，而实际上程序已经不再有变量引用它们，系统应该回收它们，此时 Python 的垃圾回收器就可能没那么15# 快，要等专门的循环垃圾回收器（Cyclic Garbage Collector）来检测并回收这种引用循环。16#17# 当一个对象被垃圾回收时，Python 就会自动调用该对象的 __del__ 方法。需要说明的是，不要以为对一个变量执行 del 操作，该变量所引用的对象就会被回收，只有18# 当对象的引用计数变成 0 时，该对象才会被回收。因此，如果一个对象有多个变量引用它，那么 del 其中一个变量是不会回收该对象的。19class Item:20 def __init__(self, name, price):21 self.name = name22 self.price = price23 # 定义析构函数24 def __del__(self):25 print('del删除对象')26# 创建一个Item对象，将之赋给im变量27im = Item('鼠标', 29.8)28x = im # ①29# 打印im所引用的Item对象30del im31print('--------------')32# 程序中重写了 Item 类的 __del__() 方法，该方法就是 Item 类的析构函数，当系统将要回收 Item 时，系统会自动调用 Item 对象的 __del__() 方法。33#34# 上面程序先创建了一个 Item 对象，并将该对象赋值给 im 变量，① 号代码又将 im 赋值给变量 x，这样程序中有两个变量引用 Item 对象，接下来程序执行35# del im 代码删除 im 对象，此时由于还有变量引用该 Item 对象，因此程序并不会回收 Item 对象。36#...

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19_在O(1)时间内删除链表结点.py

Source:19_在O(1)时间内删除链表结点.py Github

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...4class ListNode(object):5 def __init__(self, x=None):6 self.data=x7 self.next=None 8 def __del__(self):9 self.data=None10 self.next=None11class Solution(object):12 def DeleteNode(self, pListHead, pToBeDeleted):13 r"""14 Args:15 pListHead:链表的头结点16 pToBeDeleted:待删除的节点17 """18 if not pListHead or not pToBeDeleted:19 return None 20 if pToBeDeleted.next!= None: # 多个节点，删除的是中间结点21 pNext=pToBeDeleted.next 22 pToBeDeleted.data=pNext.data23 pToBeDeleted.next=pNext.next24 pNext.__del__()25 elif pListHead==pToBeDeleted: # 唯一的一个节点，要删除26 pToBeDeleted.__del__()27 pListHead.__del__()28 else: # 删除的是尾结点29 pNode=pListHead30 while pNode.next!=pToBeDeleted:31 pNode=pNode.next 32 pNode.next=None 33 pToBeDeleted.__del__()34 def DeletedNode1(self, pListHead, pToBeDeleted):35 if not pListHead and not pToBeDeleted:36 return 37 if pToBeDeleted.next!=None:38 pNext=pToBeDeleted.next39 pToBeDeleted.next=pNext.next40 pToBeDeleted.data=pNext.data41 pNext.__del__()42 elif pToBeDeleted==pListHead:43 pToBeDeleted.__del__()44 pListHead.__del__()45 else:46 pNode=pListHead47 while pNode.next!=pToBeDeleted:48 pNode=pNode.next49 pNode=None 50 pToBeDeleted.__del__()51 def DeletedNode2(self, pListHead, pToBeDeleted):52 if not pListHead and not pToBeDeleted:53 return 54 if pToBeDeleted.next!=None:55 pNext=pToBeDeleted.next56 pToBeDeleted.next=pNext.next57 pToBeDeleted.data=pNext.data58 pNext.__del__()59 elif pListHead==pToBeDeleted:60 pListHead.__del__()61 pToBeDeleted.__del__()62 else:63 pNode=pListHead 64 while pNode.next!=pToBeDeleted:65 pNode=pNode.next66 pNode=None 67 pToBeDeleted.__del__()68node1 = ListNode(10)69node2 = ListNode(11)70node3 = ListNode(13)71node4 = ListNode(15)72node1.next = node273node2.next = node374node3.next = node475S = Solution()76S.DeletedNode2(node1, node3)77print(node3.data)78S.DeletedNode2(node1, node3)79print(node3.data)80print(node2.data)81S.DeletedNode2(node1, node1)...

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SuperclassDelCalledMultipleTimes2.py

Source:SuperclassDelCalledMultipleTimes2.py Github

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1#Calling a method multiple times by using explicit calls when a base uses super()2class Vehicle(object):3 4 def __del__(self):5 recycle(self.base_parts)6 super(Vehicle, self).__del__()7 8class Car(Vehicle):9 10 def __del__(self):11 recycle(self.car_parts)12 super(Car, self).__del__()13 14 15class SportsCar(Car, Vehicle):16 17 # Vehicle.__del__ will get called twice18 def __del__(self):19 recycle(self.sports_car_parts)20 Car.__del__(self)21 Vehicle.__del__(self)22 23 24#Fix SportsCar by using super()25class FixedSportsCar(Car, Vehicle):26 27 def __del__(self):28 recycle(self.sports_car_parts)29 super(SportsCar, self).__del__()...

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multiple_del.py

Source:multiple_del.py Github

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1#Calling a method multiple times by using explicit calls when a base uses super()2class Base(object):3 def __del__(self):4 pass5class Y1(Base):6 def __del__(self):7 super(Y1, self).__del__()8class Y2(Base):9 def __del__(self):10 super(Y2, self).__del__() #When `type(self) == Y3` this calls `Y1.__del__`11class Y3(Y2, Y1):12 def __del__(self):13 Y1.__del__(self)14 Y2.__del__(self)15#Calling a method multiple times by using explicit calls when a base inherits from other base16class Z1(object):17 def __del__(self):18 pass19class Z2(Z1):20 def __del__(self):21 Z1.__del__(self)22class Z3(Z2, Z1):23 def __del__(self):24 Z1.__del__(self)...

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