Re: "Help needed - I don't understand how Python manages memory"

[Hank]

Steve Holden wrote:

>
You are suffering from a pathological condition yourself: the desire
to optimize performance in an area where you do not have any problems.
I would suggest you just enjoy using Python and then start to ask
these questions again when you have a real issue that's stopping you
from getting real work done.

regards
Steve

Hi, Steve,
This not simply a pathological condition. My people are keeping trying
many ways to have job done, and the memory problem became the focus we
are paying attention on at this moment.
Could you please give us some clear clues to obviously call python to
free memory. We want to control its gc operation handily as we were
using J**A.

[sturlamolden]

On Apr 20, 9:09 pm, "Hank @ITGroup" <hank.info...@g mail.comwrote:

Could you please give us some clear clues to obviously call python to
free memory. We want to control its gc operation handily as we were
using J**A.

If you want to get rid of a Python object, the only way to do that is
to get rid of every reference to the object. This is no different from
Java.

If you just want to deallocate and allocate memory to store text,
Python lets you do that the same way as C:
from __future__ import with_statement
import os
from ctypes import c_char, c_char_p, c_long, cdll
from threading import Lock

_libc = cdll.msvcr71 if os.name == 'nt' else cdll.libc
_lock = Lock()

def string_heapallo c(n):
''' allocate a mutable string using malloc '''
with _lock:
malloc = _libc.malloc
malloc.argtypes = [c_long]
malloc.restype = c_char * n
memset = _libc.memset
memset.restype = None
memset.argtypes = [c_char * n, c_char, c_long]
tmp = malloc(n)
memset(tmp,'0', n)
return tmp

def string_heapfree (s):
''' free an allocated string '''
with _lock:
free = _libc.free
free.restype = None
free.argtypes = [c_char_p]
ptr_first_char = c_char_p( s[0] )
free(ptr_first_ char)
if __name__ == '__main__':
s = string_heapallo c(1000)
s[:26] = 'abcdefghijklmn opqrstuvwxyz'
print s[:]
string_heapfree (s)

[Gabriel Genellina]

En Sun, 20 Apr 2008 17:19:43 -0300, sturlamolden <st**********@y ahoo.noescribió :

On Apr 20, 9:09 pm, "Hank @ITGroup" <hank.info...@g mail.comwrote:

>Could you please give us some clear clues to obviously call python to
free memory. We want to control its gc operation handily as we were
using J**A.

If you want to get rid of a Python object, the only way to do that is
to get rid of every reference to the object. This is no different from
Java.

If you just want to deallocate and allocate memory to store text,
Python lets you do that the same way as C:

I'm not sure if this will help the OP at all - going into a world of dangling pointers, keeping track of ownership, releasing memory by hand... One of the good things of Python is automatic memory management. Ensuring that all references to an object are released (the standard Python way) is FAR easier than doing all that by hand.

--
Gabriel Genellina

[sturlamolden]

On Apr 21, 4:09 am, "Gabriel Genellina" <[e-mail].a r>
wrote:

I'm not sure if this will help the OP at all - going into a world of dangling pointers, keeping track of ownership, releasing memory by hand... One of the good things of Python is automatic memory management. Ensuring that all references to an object are released (the standard Python way) is FAR easier than doing all that by hand.

The owner was complaining he could not manually release memory using
del, as if it was Python's equivalent of a C++ delete[] operator. I
showed him how it could be done. I did not say manual memory
management is a good idea.