index of min element of sequence

[Neal Becker]

What's a good/fast way to find the index of the minimum element of a
sequence? (I'm fairly sure sorting the sequence is not the fastest
approach)

 

[Peter Otten]

What's a good/fast way to find the index of the minimum element of a
sequence? (I'm fairly sure sorting the sequence is not the fastest
approach)

items = "defbhkamnz"
min(xrange(len(items)), key=items.__getitem__) 6
items[6]

'a'

Peter

 

[Paul Rubin]

What's a good/fast way to find the index of the minimum element of a
sequence? (I'm fairly sure sorting the sequence is not the fastest
approach)

Python 2.5 (untested):

from operator import itemgetter
minindex = min(enumerate(seq), key=itemgetter(1))[1]

 

[Roger Miller]

....

....

Or just
items.index(min(items))
I found this to be significantly faster in a simple test (searching a
list of 1000 ints with the minimum in the middle), despite the fact
that it requires two passes. I'm sure that one could find cased where
Peter's approach is faster, so you if you are concerned about speed
you should measure with your own data.

 

[John Machin]

What's a good/fast way to find the index of the minimum element of a
sequence? (I'm fairly sure sorting the sequence is not the fastest
approach)

Python 2.5 (untested):

from operator import itemgetter
minindex = min(enumerate(seq), key=itemgetter(1))[1]
Bzzzt!

seq = [1000, 9, 8, 7, 2000, 3000]
from operator import itemgetter
minindex = min(enumerate(seq), key=itemgetter(1))[1]
minindex 7
min(enumerate(seq), key=itemgetter(1))

(3, 7)

s/[1]/[0]/ or more generally:

minindex, minvalue = min(enumerate(seq), key=itemgetter(1))

 

[Peter Otten]

...

Or just
items.index(min(items))
I found this to be significantly faster in a simple test (searching a
list of 1000 ints with the minimum in the middle), despite the fact
that it requires two passes. I'm sure that one could find cased where
Peter's approach is faster, so you if you are concerned about speed
you should measure with your own data.

I suppose those cases are rare (slow equality check), and even then I
might prefer your solution because it's so much clearer.

Peter

 

[Paul Rubin]

s/[1]/[0]/ or more generally:

Oops, got two spellings confused. Originally was going to use

from itertools import count, izip
min(izip(seq, count()))[1]

but did it with enumerate instead. I don't know which is actually
faster.

minindex, minvalue = min(enumerate(seq), key=itemgetter(1))

Cool, I like this best of all. Or alternatively,

minindex, minvalue = min(izip(seq, count()))

 

[John Machin]

s/[1]/[0]/ or more generally:

Oops, got two spellings confused. Originally was going to use

from itertools import count, izip
min(izip(seq, count()))[1]

but did it with enumerate instead. I don't know which is actually
faster.

minindex, minvalue = min(enumerate(seq), key=itemgetter(1))

Cool, I like this best of all. Or alternatively,

minindex, minvalue = min(izip(seq, count()))

Bzzzt #2!
(7, 3)

 

[Paul Rubin]

(7, 3)

Serves me right for cutting and pasting.

minvalue, minindex = min(izip(seq, count()))