import sysclass A(): def __init__(self): '''初始化对象''' print('object born id:%s' %str(hex(id(self))))def f1(): '''循环引用变量与删除变量''' while True: c1=A() del c1def func(c): print('obejct refcount is: ',sys.getrefcount(c)) #getrefcount()方法用于返回对象的引用计数if __name__ == '__main__': #生成对象 a=A() # 此时为1 #del a # 如果del,下一句会报错, = 0,被清理 print('obejct refcount is: ', sys.getrefcount(a)) # 此时为2 getrefcount是一个函数 +1 func(a) #增加引用 b=a func(a) #销毁引用对象b del b func(a)
执行结果:
object born id:0x7f9abe8f2128 obejct refcount is: 2 obejct refcount is: 4 obejct refcount is: 5 obejct refcount is: 4
导致引用计数 +1 的情况
对象被创建,例如 a=23
对象被引用,例如 b=a
对象被作为参数,传入到一个函数中,例如func(a)
对象作为一个元素,存储在容器中,例如list1=[a,a]
导致引用计数-1 的情况
对象的别名被显式销毁,例如del a
对象的别名被赋予新的对象,例如a=24
一个对象离开它的作用域,例如 f 函数执行完毕时,func函数中的局部变量(全局变量不会)
对象所在的容器被销毁,或从容器中删除对象
循环引用导致内存泄露
def f2(): '''循环引用''' while True: c1=A() c2=A() c1.t=c2 c2.t=c1 del c1 del c2
执行结果
id:0x1feb9f691d0 object born id:0x1feb9f69438 object born id:0x1feb9f690b8 object born id:0x1feb9f69d68 object born id:0x1feb9f690f0 object born id:0x1feb9f694e0 object born id:0x1feb9f69f60 object born id:0x1feb9f69eb8 object born id:0x1feb9f69128 object born id:0x1feb9f69c88 object born id:0x1feb9f69470 object born id:0x1feb9f69e48 object born id:0x1feb9f69ef0 object born id:0x1feb9f69dd8 object born id:0x1feb9f69e10 object born id:0x1feb9f69ac8 object born id:0x1feb9f69198 object born id:0x1feb9f69cf8 object born id:0x1feb9f69da0 object born id:0x1feb9f69c18 object born id:0x1feb9f69d30 object born id:0x1feb9f69ba8 ...