need the average from a list of timedelta objects

Question

I have created a list of timedelta objects and i need to get the average of this list. when i try to do

return (sum(delta_list)/(len(delta_list)-1))

i get

TypeError: unsupported operand type(s) for +: 'int' and 'datetime.timedelta'

I am new at working with python's datetime classes. I also would like to know how to get this average into a format like days: hours: mins: i don't need anything smaller than mins.

Answer 1

sum wants a starting value, which is 0 by default, but 0 can't be added to a timedelta so you get the error.

You just have to give sum a timedelta() as the start value:

# this is the average
return sum(delta_list, timedelta()) / len(delta_list)

To print it out you can do this:

print str(some_delta)

If you want something customized you can get some_delta.days and some_delta.seconds but you have to calculate everything between.

Answer 2

First of all, sum adds all of the elements from the list to an initial value, which is by default 0 (an integer with value of zero). So to be able to use sum on a list of timedelta's, you need to pass a timedelta(0) argument - sum(delta_list, timedelta(0)).

Secondly, why do you want to subtract one from the length of the list? If a list is of length 1 you'll get a ZeroDivisionError.

Having fixed the above you'll end up with a timedelta object being an average. How to convert that to a human-readable format I'm leaving for you as an exercise. The datetime module documentation should answer all of the possible questions.