Original Page: http://blog.modp.com/2008/09/sorting-python-dictionary-by-value-take.html
Here’s why another reason why you should blog all your technical problems and solutions. Sometimes someone finds a better way.
In my original sorting a dict by value entry, I said the best way is:
sorted(adict.iteritems(), key=lambda (k,v): v)
Turns out I’m wrong. Gregg Lind (aka “write-only") replied to the article with a comment pointing to his performance notes. PEP 0265 has the “best answer" that is at least 2x faster:
from operator import itemgetter sorted(d.iteritems(), key=itemgetter(1))
Thanks all!
My performance test is here:
#!/usr/bin/env python
import cProfile
def sbv0(adict,reverse=False):
return sorted(adict.iteritems(), key=lambda (k,v): v, reverse=reverse)
from operator import itemgetter
def sbv6(d,reverse=False):
return sorted(d.iteritems(), key=itemgetter(1), reverse=reverse)
imax= 10000
dmax = 500
D = dict(zip([str(i) for i in range(dmax)],range(dmax)))
cProfile.run('for i in xrange(imax): sbv0(D, reverse=False)')
cProfile.run('for i in xrange(imax): sbv6(D, reverse=False)')
Results are
Old Way:
5020002 function calls in 6.623 CPU seconds
New Way:
20002 function calls in 3.920 CPU seconds
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