En Tue, 18 Nov 2008 08:41:58 -0200, Paul Rubin
<"http://phr.cx"@nospam.invalid> escribió:
[EMAIL PROTECTED] writes:
but how do I then do a secondary sort by the imaginary part,...
Is there a way to do this using just the key arg, no extra data
structures?
Clever solutions involving multiple sorts aside, I think what they
really want you to do is something like (untested):
class mkKey(complex):
def __lt__(self, other):
a = cmp(self.real, other.real)
return a if a else cmp(self.imag, other.imag)
then:
yourlist.sort(key=mkKey)
for fancier structures you'd need a full blown class implementation
with an init method. Either way you end up temporarily allocating a
lot of extra structures, but at least they're not all in memory
simultaneously like in the DSU pattern.
Yes, the keys for all items in the list are all created when the sort
begins, and live until the sort finishes. list.sort(key=...) is actually
implemented using the DSU pattern, something like this:
for i in range(len(alist)):
alist[i] = (key(alist[i]), alist[i])
# ...sort items...
for i in range(len(alist)):
alist[i] = alist[i][1]
except a custom `sortwrapper` object is used instead of a 2-item tuple.
--
Gabriel Genellina
--
http://mail.python.org/mailman/listinfo/python-list
