[EMAIL PROTECTED] wrote:
Hello,
I have a long list of memory-heavy objects that I would like to access
in differently sorted order. Let's say I'd like to have lists called
by_date or by_size that I can use to access the objects in the
specified order.
Of course I can just build those lists naively by creating copies of
the original list and then sorting them according to my wishes. But
that would create huge memory overhead. Of course I could use lists of
indices into the "master" list, just as in C I'd create lists or
arrays of pointers into the original data.
Is there a clever Python way to do this, or should I just use lists of
indices?
No need. A Python list contains *references* to objects, not copies of
objects. (The same is true of variables, dictionaries, sets, and so
on...).
For example, in the following code, only one copy of HeavyObject
exists, however, it is referred to many times.
a = HeavyObject()
b = a
A = [a,b]
B = [b,a]
C = set([a,b])
D = {1:a, 2:b}
... and do on
Implementation wise, a long list consumes about 4 bytes per list element
(that's one address per), plus a tine amount of overhead.
Gary Herron
I know there is a thing called "shallow copy" that has something to do
with not duplicating memory content but I don't understand the
concept. Maybe that's what would help here, too.
Thanks,
robert
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