来自sys.getrefcount的意外结果

问题描述

当我输入时：

  
它不是 astrd 但值 123 。  astrd 仅仅是（不可变的）数字123的名称，可以多次引用。除此之外，小整数通常是共享的： 
 
 
 >>> astrd = 123 
>>> sys.getrefcount（astrd）
 4 
>>> j = 123 
>>> sys.getrefcount（astrd）
 5 
  
在第二个任务中，没有创建新的整数，而不是 j 只是整数 123 的新名称。
 
 
 
然而，给定非常大的整数，这并不成立： 
 
 
 >>> i = 823423442583 
>>> sys.getrefcount（i）
 2 
>>> j = 823423442583 
>>> sys.getrefcount（i）
 2 
  
共享整数是CPython的实现细节其他）。由于小整数经常被实例化，共享它们会节省大量的内存。这是因为整数是不可变的这一事实。
 
 
 
有关第二个示例中的附加参考，请参阅参考资料。 。
 
When I typed:
>>> astrd = 123
>>> import sys
>>> sys.getrefcount(astrd)
3
>>>
I am not getting where is astrd used 3 times ?
 解决方案 
It's not astrd that is referenced three times, but the value 123. astrd is simply a name for the (immutable) number 123, which can be referenced however many times. Additionally to that, small integers are usually shared:
>>> astrd = 123
>>> sys.getrefcount(astrd)
4
>>> j = 123
>>> sys.getrefcount(astrd)
5
In the second assignment, no new integer is created, instead j is just a new name for the integer 123.
However, given very large integers, this does not hold:
>>> i = 823423442583
>>> sys.getrefcount(i)
2
>>> j = 823423442583
>>> sys.getrefcount(i)
2
Shared integers are an implementation detail of CPython (among others). Since small integers are instantiated very often, sharing them saves a lot of memory. This is made possible by the fact that integers are immutable in the first place.
For the additional reference in the second example, cf. codeape's answer.
                        
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