attribute assignment effects all class instances

[Andrew Durdin]

On Thu, 09 Sep 2004 19:14:20 -0700, Jeff Shannon <jeff at ccvcorp.com> wrote:
> And since others have already told you *why* you're having a problem,
> I'll limit myself to showing you one possible way around that problem.

And for another way around: just change the line in __init__ from
    self.adjacent = adjacent
To
    self.adjacent = list(adjacent)

This will alter the overall behaviour -- the new node will always make
a copy of the list. An example is best to show the difference. Suppose
you have the following code:

adj = [node1, node2, node3, node4]
newnode1 = node(adjacent=adj)
newnode2 = node(adjacent=adj)
...  # Some other irrelevant code
newnode2.adjacent[left] = node5

With Jeff's solution (and your original), newnode1.adjacent will also
have changed, so will be [node1, node5, node3, node4]. With the
solution above which copies the list, newnode1 will not have changed.

The solution you should use depends on what behaviour you want for
this situation.