python __del__() 清空对象

osc_ozapt2g1 2020-11-17 08:41:49
Python def


python __del__() 清空对象

python垃圾回收机制:当一个对象的引用被完全清空之后,就会调用__del__()方法来清空这个对象

当对象的引用没有被完全清空时,代码如下:

class C():
def __init__(self):
print('调用构造器创建对象')
def __del__(self):
print('销毁创建的对象')
c1 = C()
c2 = c1
c3 = c1
print('=====================================')
print(str(id(c1)) +' , '+ str(id(c2)) +' , '+ str(id(c3)))
print('=====================================')
del c1
del c2
# del c3 先保留c3,不完全删除C()的引用
# print(c1) 不注释的话会报错:NameError: name 'c1' is not defined
# print(c2) 不注释的话会报错:NameError: name 'c2' is not defined
print(c3) # 输出:<__main__.C object at 0x0000023444AF0AC0>
print('=====================================')
while True:
time.sleep(2)
print('循环中.......')

输出结果: 下面的输出结果里面没有显示 “销毁创建的对象”

调用构造器创建对象
=====================================
2423513877184 , 2423513877184 , 2423513877184
=====================================
<__main__.C object at 0x0000023444AF0AC0>
=====================================
循环中.......
循环中.......
循环中.......
循环中.......

 

当对象的引用完全被清空时,代码如下:

class C():
def __init__(self):
print('调用构造器创建对象')
def __del__(self):
print('销毁创建的对象')
c1 = C()
c2 = c1
c3 = c1
print('=====================================')
print(str(id(c1)) +' , '+ str(id(c2)) +' , '+ str(id(c3)))
print('=====================================')
del c1
del c2
del c3 #已经将对象的引用全部删除,程序会自动调用 __del__方法
# print(c1) 不注释的话会报错:NameError: name 'c1' is not defined
# print(c2) 不注释的话会报错:NameError: name 'c2' is not defined
# print(c3) 不注释的话会报错:NameError: name 'c3' is not defined
print('=====================================')
while True:
time.sleep(2)
print('循环中.......')

输出结果:

调用构造器创建对象
=====================================
2873013504704 , 2873013504704 , 2873013504704
=====================================
销毁创建的对象
=====================================
循环中.......
循环中.......
循环中.......
循环中.......

 

版权声明
本文为[osc_ozapt2g1]所创,转载请带上原文链接,感谢
https://my.oschina.net/u/4416751/blog/4720628

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