returning index of minimum in a list of lists

[forman.simon at gmail.com]

JJLaRocque at gmail.com wrote:
> Hi all,
> Is there a simple python function to return the list index of the
> minimum entry in a list of lists?
> ie, for   [[3,3,3,3], [3,3,3,1], [3,3,3,3]]  to return 2,4.
> Or, same question but just for a list of numbers, not a list of lists.
> Thanks,
> Josh

One way to do this is to generate (value, index-in-main-list,
index-in-secondary-list) tuples and then just take the minimum.

def f(L):
    '''Return indices of the first minimum value in a list of lists.'''
    return min(
        (n, i, j)
        for i, L2 in enumerate(L)
        for j, n in enumerate(L2)
        )[1:]

L = [[3, 3, 3, 3], [3, 3, 3, 1], [3, 3, 3, 3]]

print f(L) # prints (1, 3)

Note: In python (and most other languages) indices begin at 0, so your
return values of (2, 4) wouldn't be correct.

For a list of numbers it's simpler.

L = [3, 3, 3, 1, 3, 3]
print min((n, i) for i, n in enumerate(L))[1] # prints 3

Hope this helps

~Simon