[Python-Dev] PEP 42: sizeof(obj) builtin

[M.-A. Lemburg]

M.-A. Lemburg wrote:
> Tim Peters wrote:
> 
>> [Raymond Hettinger]
>>
>>> I'm about to start working on this one and wanted
>>> to check here first to make sure there is still a
>>> demand for it and to get ideas on the best implementation
>>> strategy.
>>
>> Marc-Andre implemented it for mxTools:
>>
>>     http://www.lemburg.com/files/python/mxTools.html
>>
>>     sizeof(object)
>>
>>     Returns the number of bytes allocated for the given Python object.
>>     Additional space allocated by the object and stored in pointers is 
>> not
>>     taken into account (though the pointer itself is). If the object
>>     defines tp_itemsize in its type object then it is assumed to be a
>>     variable size object and the size is adjusted accordingly.
>>
>> I don't know whether anyone finds it useful in real life; maybe MAL 
>> has an
>> idea about that.
> 
> Some do; I wrote this for cache management to at least
> have a hint at the memory size being used by the objects in
> the cache.

FWIW, here's something Dirk Holtwick started working on.

import struct
sizeof_PyObject = len(struct.pack('P', 0))

def calcsize(i, s=0):
     s = sizeof(i)
     if type(i) == type({}):
         s += (len(i) * 2 * sizeof_PyObject)
         # guess table size
         s += (len(i) * sizeof_PyObject * 2) / 3
         for k, v in i.items():
             s += calcsize(k)
             s += calcsize(v)
     elif type(i) == type([]):
         for v in i:
             s += calcsize(v)
             s += 1 * sizeof_PyObject
     elif type(i) == type((1,)):
         for v in i:
             s += calcsize(v)
     return s

I'm sure this could easily be turned into a std lib module
which then covers all the Python builtins....
  --
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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