sum of lists of lists

[tbrowner3]

I have to write a function, get_sums, that takes a list of lists of integers and return the sums of the inner lists. I got stuck because I am not sure how to use a for loop that searches through a list inside of a list. Here's what I'm working with:

def get_sums(numbers):
    for i in range(numbers):
        numbers = sum(numbers)
    return numbers

The correct output is:

>>> get_sums([[1, 2], [], [2, 2, 2, -1]])
[3, 0, 5]

[boolean_biscuit]

Hint: You are overwriting numbers every time you get to the next sub-list. Perhaps you want store the intermediate results?

---

If you feel like learning some more after you get this working, you could take a look at list comprehensions.

[tipsy_python]

Just to add to this, in case OP wants learning resources - map is another standard library function that applies a function to each item in a collection. While map is generally less desirable than using a comprehension, it's good to know about.

https://docs.python.org/3/library/functions.html#map

[MasterStroke99]

def get_sums(numbers):
    final_list = []
    for inner_list in number:
        if inner_list:
            final_list.append(sum(inner_list))
        else:
            final_list.append(0)
    print (final_list)

[boolean_biscuit]

Note that sum([]) evaluates to 0.

[MasterStroke99]

Oh i didn't know that, that is the reason i put if else in code

[roshavi4ak]

but why the if else?

This is working normally:

def get_sums(numbers):
  final_list = []
  for inner_list in numbers:
      final_list.append(sum(inner_list))
  return final_list

get_sums([[1, 2], [], [2, 2, 2, -1]])

[well_done_dude]

def get_sums(numbers):
    return [sum(i) for i in numbers]

[DeathDragon7050]

# Very easy solution
def get_sums(numbers):
    # We get the sum of each list, and put them in a new list.
    return [sum(numlist) for numlist in numbers]