why does memory consumption keep growing?

[Chris Angelico]

On Fri, Oct 6, 2017 at 8:06 AM, Fetchinson . via Python-list
<python-list at python.org> wrote:
> Hi folks,
>
> I have a rather simple program which cycles through a bunch of files,
> does some operation on them, and then quits. There are 500 files
> involved and each operation takes about 5-10 MB of memory. As you'll
> see I tried to make every attempt at removing everything at the end of
> each cycle so that memory consumption doesn't grow as the for loop
> progresses, but it still does.
>
> import os
>
> for f in os.listdir( '.' ):
>
>     x = [ ]
>
>     for ( i, line ) in enumerate( open( f ) ):
>
>         import mystuff
>         x.append( mystuff.expensive_stuff( line ) )
>         del mystuff
>
>     import mystuff
>     mystuff.some_more_expensive_stuff( x )
>     del mystuff
>     del x
>
>
> What can be the reason? I understand that mystuff might be leaky, but
> if I delete it, doesn't that mean that whatever memory was allocated
> is freed? Similary x is deleted so that can't possibly make the memory
> consumption go up.

You're not actually deleting anything. When you say "del x", all
you're doing is removing the *name* x. Especially, deleting an
imported module basically does nothing; it's a complete waste of time.
Modules are kept in their own special cache.

ChrisA