[Tutor] python memory management

[Alan Gauld]

On 03/09/16 23:20, zakaria wrote:
> Is there any practical usage of using reference cycling?

There are a (very) few cases where data structures require the
creation of cyclic references. One example I've used is in
managing comms networks where nodes are multiply and/or
cyclically linked and you need to build those linkages into
your data model. In those cases you need to manage the
cleanup yourself.

But most cyclic references occur by accident, the programmer
probably didn't intend them to exist but it just so happened that
one object points to another which happens to point at another
which in turn points at the first. The cycle can span many objects.
Think of a directory tree where a deeply nested node has a link
pointing back at a root level node. But the root also indirectly
points at that low level node by means of the tree structure...

As a specific example, It often happens in GUIs where widgets
hold references to other widgets higher in the widget
parent/child tree.

-- 
Alan G
Author of the Learn to Program web site
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