On Thu, 12 Apr 2007 07:37:38 +0000, Antoon Pardon wrote:
> I once had a problem I like to solve by having a dictionary
> where the keys were multidimensional points on an integer grid.
> For a number of reasons I thought it would be easier if I could
> use lists, but most people argued that would be a bad idea and
> that I should use tuples, because they are immutable.
Also because code that raises "TypeError: list objects are unhashable" is
probably not going to work very well.
> Of course if I now would want to find out if the point is on an axis and
> which axis that is, I cannot use index because that is not available.
If memory is more important to you than speed:
class IndexTuple(tuple):
def index(self, target):
for i, x in enumerate(self):
if x == target: return i
raise ValueError
Or if speed is more important to you than memory:
class IndexTuple2(tuple):
def index(self, target):
return list(self).index(target)
If you prefer not to subclass, you can write an index function:
def index(sequence_or_mapping, target):
try:
return sequence_or_mapping.index(target)
except AttributeError:
return list(sequence_or_mapping).index(target)
So much fuss over such a little thing... yes it would be nice if tuples
grew an index method, but it isn't hard to work around the lack.
--
Steven.
--
http://mail.python.org/mailman/listinfo/python-list
