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rew
Asked:2023-08-19 19:46:31 +0000 UTC2023-08-19 19:46:31 +0000 UTC

导入math模块时，None对象的引用数量减少

  • 772

我注意到一个有趣的行为，但我无法理解。

导入模块时，math对象引用的数量None会减少：

import sys

print(sys.getrefcount(None))
import math
print(sys.getrefcount(None))

结论：

4138
4099

为什么会发生这种情况变得很有趣。如果有人能解释我会很高兴）

python

2 个回答

  1. Best Answer

    正如专业人士所说：

    我认为这只是Python 3.8 中填充的方法缓存。当缓存条目被填满时，它会删除对 None 的引用，转而保存对字符串的引用。

    一点 printf 调试表明了这一点：

    >>> import math
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\listobject.c:2488
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\listobject.c:2488
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\compile.c:1331
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\compile.c:1331
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2373
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:6805
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2373
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:6805
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3390
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3391
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
INCREF None
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2373
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2373
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2373
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:6805
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3390
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3391
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\typeobject.c:3160
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:4971
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2978
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2979
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\frameobject.c:430
INCREF None
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2373
INCREF None
INCREF None
INCREF None
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3390
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3391
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:1363
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\weakrefobject.c:939
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Objects\funcobject.c:585
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3390
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:3391
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\ceval.c:2995
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Include\object.h:560
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\pythonrun.c:268
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Modules\_io\bufferedio.c:804
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\pythonrun.c:1126
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Modules\_io\bufferedio.c:804
INCREF None
DECREF None at C:\Users\sween\Source\Repos\cpython2\cpython\Python\pythonrun.c:1134

    翻译：

    我认为它只是填充 Python 3.8 中的方法缓存。当缓存条目填满时，它会删除对 None 的引用，而是包含对字符串的引用。

    一些调试 printf 显示了这一点：

    -- 修剪过 --

    也就是说，事实是 math 没有足够的方法缓存（方法缓存），它从那里删除了不必要的 None 。

    • 6

  2. 当然，我不是专家，但在我看来，它math需要大量的内存，但None最不必要的操作符。尝试创建一个函数，导入后math，链接会再次减少。

    import sys

print(sys.getrefcount(None))
import math
print(sys.getrefcount(None))
def no():
    pass
print(sys.getrefcount(None))
    • 3

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