On Fri, 11 Nov 2005, Chris Stiles wrote:
> Is there an easier and cleaner way of doing this ? Is there example
> code floating around that I might have a look at ?
I'm not aware of a way which can honestly be called better.
However, i do feel your pain about representing the alias relationships
twice - it feels wrong. Therefore, i offer you an alternative
implementation - represent each set as a linked list, threaded through a
dict by making the value the dict holds under each key point to the next
key in the alias set. Confused? No? You will be ...
class Aliases(object):
def __init__(self, aliases=None):
self.nexts = {}
if (aliases != None):
for key, value in aliases:
self[key] = value
def __setitem__(self, key, value):
if ((value != None) and (value != key)):
self.nexts[key] = self.nexts[value]
self.nexts[value] = key
else:
self.nexts[key] = key
def __getitem__(self, key):
return list(follow(key, self.nexts))
def __delitem__(self, key):
cur = key
while (self.nexts[cur] != key):
cur = self.nexts[cur]
if (cur != key):
self.nexts[cur] = self.nexts[key]
del self.nexts[key]
def canonical(self, key):
canon = key
for cur in follow(key, self.nexts):
if (cur < canon):
canon = cur
return canon
def iscanonical(self, key):
for cur in follow(key, self.nexts):
if (cur < key):
False
return True
def iteraliases(self, key):
cur = self.nexts[key]
while (cur != key):
yield cur
cur = self.nexts[cur]
def __iter__(self):
return iter(self.nexts)
def itersets(self):
for key in self.nexts:
if (not isprimary(key, self.nexts)):
continue
yield [key] + self[key]
def __len__(self):
return len(self.nexts)
def __contains__(self, key):
return key in self.nexts
def __str__(self):
return "<Aliases " + str(list(self.itersets())) + ">"
def __repr__(self):
return "Aliases([" + ", ".join(str((key, self.canonical(key)))
for key in sorted(self.nexts.keys())) + "])"
As i'm sure you'll agree, code that combines a complete absence of clarity
with abject lack of runtime efficiency. Oh, and i haven't tested it
properly.
tom
--
if you can't beat them, build them
--
http://mail.python.org/mailman/listinfo/python-list
