File Closing Problem in 2.3 and 2.4, Not in 2.5 (Final report)

[Gabriel Genellina]

At Tuesday 9/1/2007 22:03, Carroll, Barry wrote:

>The first assumption was correct: the file object is destroyed.  The 
>second assumption is apparently incorrect: the file handle is not 
>released when the associated object is destroyed.  These 'orphaned' 
>file handles build up and when the OS handle limit is reached, "too 
>many open files" errors show up.

I've tried with 2.3.4 something like this:

   flist = []
   for i in range(5000):
     fn = 'test%04.4d.tmp' % i
     print fn
     f = open(fn,'w')
     flist.append(f)
     # f.close()

Without the last close(), I get an error on iteration 509 like you; 
adding the close(), I can create the 5000 file instances without 
problems. So it seems that Python *does* release the file handle.

> > On Python 2.5 you can use the new `with` statement.
> >
>
>Not only that, the file errors don't appear when we run our 
>program/table combination under 2.5.  I can't explain the 
>difference, unless the work done to implement the 'with' statement 
>has an impact outside the scope of that feature.  In any event, it 
>does us no good.  Other constraints on the test system require us to 
>stick with Python 2.3, at least for the present.

My advise would be (as others have already suggested) to not *assume* 
anything and put a print statement when you think you close the file. 
Perhaps that code fragment is never executed! Or perhaps there is 
*another* place where you open a file and never close it (a logfile 
perhaps? it doesnt have to be a different file each time). Someone 
already suggested to use Filemon to trace the file operations; you 
can also use Process Explorer to inspect the open file handles (both 
tools available from SysInternals).


-- 
Gabriel Genellina
Softlab SRL 


	

	
		
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