Python Find index of minimum item in list of floats

Question

How can I find the index of the minimum item in a Python list of floats  If they were integers  I would simply do   minIndex   myList index min myList     However  with a list of floats I get the following error  I assume because float equality comparison is rather iffy   ValueError  0 13417985135 is not in list   Now  I know that I could simply scroll through the list and compare each item to see whether it is  lt   min   0 0000000000001  and    min - 0 0000000000001   but that is kinda messy  Is there a more elegant  preferably built-in  way to find the index of the smallest item in a list of floats

User · Answer

I would use   val  idx   min  val  idx  for  idx  val  in enumerate my list     Then val will be the minimum value and idx will be its index

User · Answer

You re effectively scanning the list once to find the min value  then scanning it again to find the index  you can do both in one go   from operator import itemgetter min enumerate a   key itemgetter 1   0

User · Answer

I think it s worth putting a few timings up here for some perspective   All timings done on OS-X 10 5 8 with python2 7  John Clement s answer   python -m timeit -s  my list   range 1000    -1   from operator import itemgetter   min enumerate my list  key itemgetter 1    1000 loops  best of 3  239 usec per loop       David Wolever s answer   python -m timeit -s  my list   range 1000    -1    min  val  idx  for  idx  val  in enumerate my list   1000 loops  best of 3  345 usec per loop   OP s answer   python -m timeit -s  my list   range 1000    -1    my list index min my list    10000 loops  best of 3  96 8 usec per loop   Note that I m purposefully putting the smallest item last in the list to make  index as slow as it could possibly be   It would be interesting to see at what N the iterate once answers would become competitive with the iterate twice answer we have here   Of course  speed isn t everything and most of the time  it s not even worth worrying about     choose the one that is easiest to read unless this is a performance bottleneck in your code  and then profile on your typical real-world data -- preferably on your target machines

User · Answer

Use of the argmin method for numpy arrays   import numpy as np np argmin myList    However  it is not the fastest method  it is 3 times slower than OP s answer on my computer  It may be the most concise one though

[python] Python: Find index of minimum item in list of floats

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