On Jan 28, 4:37 am, John O'Hagan <m...@johnohagan.com> wrote:
> On Tue, 27 Jan 2009, Reckoner wrote:
> > I'm not sure this is possible, but I would like to have
> > a list of objects
>
> > A=[a,b,c,d,...,z]
>
> > where, in the midst of a lot of processing I might do something like,
>
> > A[0].do_something_which_changes_the_properties()
>
> > which alter the properties of the object 'a'.
>
> > The trick is that I would like A to be mysteriously aware that
> > something about the object 'a' has changed so that when I revisit A,
> > I will know that the other items in the list need to be refreshed to
> > reflect the changes in A as a result of changing 'a'.
>
> > Even better would be to automatically percolate the subsequent changes
> > that resulted from altering 'a' for the rest of the items in the list.
>
> [...]
>
> Interesting question.
>
> Maybe this is too simple for your purpose (or maybe just wrong!), but could
> you subclass list and give it an "update" method which keeps a dictionary of
> the state of its members and/or calls another method that makes the
> appropriate changes in the other members when a change occurs, something
> like:
>
> class SelfAwareList(list):
>
> state_dict = {}
>
> def update(self):
> for i in self:
> if i.state == 'some_condition':
> self.do_stuff_to_other_members()
> self.state_dict[i] = i.state
>
> def do_stuff_to_other_members(self):
> print 'doing stuff...'
>
> ?
>
> You could manually call update() on the SelfAwareList instance after calling a
> method on a SelfAwareList member, or even build it into the members' methods
> so that it was automatic.
>
> HTH,
>
> John
Hi Reckoner & John O'Hagan,
Great thread, very interesting.
John, I haven't seen anything like your class that uses list instead
of object and refers to state directly (i.state in self). Could you
elaborate? Here would be my implementation of your idea:
class SelfAwareList2(object):
def __init__(self, l):
self.l = l
self.changed = [False for element in l]
def __str__(self):
return str(self.l)
def update(self, index, value):
self.l[index] = value
self.changed[index] = True
def do_stuff_to_other_members(self):
for i in self.changed:
if i==False:
self.l[i] += 1
Here you can print and whenever you update your list, self.changed
keeps track of what changed. Later on you can call do_stuff_to_others
which in this case adds 1 to each other element.
I assume that your class replaces the awkwardness of l.update(0, 5)
with l[0] = 5, but I can't quite wrap my mind around it.
Luther.
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