Sorting tuples
Jeff Bauer
jbauer at rubic.com
Sun Apr 18 20:32:54 EDT 1999
> I have a list of tuples
> [('a','p','q'),('b','r','s'),('c','t','u'),('a','v','w'),('b','x','y')],
> and I want to print out
>
> a : p, q, v, w
> b : r, s, x, y
> c : t, u
Jon,
There are lots of cute ways to do this, and I
expect to see a bunch of followup posts that will
show off arcane Python wizardry, but the simple
solution is to use a dictionary.
The dictionary approach is quick, easy, and
more amenable to modification.
### Jon's list of tuples, shuffled
t = [ ('b','y','x'),
('a','v','w'),
('b','r','s'),
('c','u','t'),
('a','p','q'), ]
### build the dict
d = {}
for x in t:
if not d.has_key(x[0]):
d[x[0]] = []
for y in x[1:]:
d[x[0]].append(y)
### print the dict, sorting the values at the
### last possible moment.
keys = d.keys()
keys.sort()
for k in keys:
d[k].sort()
print k, ':', d[k]
It may not be obvious from the example above, but lists
of tuples can also just be sorted in place, e.g.
t = [ ('b','x','y'), ...
t.sort()
Python almost always follows the principle of least
surprise in this regard.
Best regards,
Jeff Bauer
Rubicon, Inc.
More information about the Python-list
mailing list