Alan G Isaac
1/25/2008 4:57:00 PM
I have a small set of objects associated with a larger
set of values, and I want to map each object to its
minimum associated value. The solutions below work,
but I would like to see prettier solutions...
Thank you,
Alan Isaac
===================================================================
import time, random
from itertools import groupby
from collections import defaultdict
class Pass:
pass
# arbitrary setup
keys = [Pass() for i in range(10)]*3
vals = [random.random() for i in range(30)]
kv = zip(keys,vals)
random.shuffle(kv)
#OBJECTIVE:
# find minimum val associated with each "key" in kv
print "method 1: brute force"
t=time.clock()
d = dict()
for k,v in kv:
if k in d:
if d[k] > v:
d[k] = v
else:
d[k] = v
print time.clock()-t
print d
print
print "method 2: groupby"
t=time.clock()
d = dict()
kv_sorted = sorted(kv, key=lambda x: id(x[0]))
for k, g in groupby( kv_sorted, key=lambda x: x[0] ):
d[k] = min(gi[1] for gi in g)
print time.clock()-t
print d
print
print "method 3: defaultdict"
t=time.clock()
d = defaultdict(list)
for k,v in kv:
d[k].append(v)
for k in d:
d[k] = min(d[k])
print time.clock()-t
print d