how to print a list containing the separate sums of lists

Question

I'm trying to gain the sum of a list of lists where the output would be [6,2,10] for the defined lists below.

data = [[1,2,3], [2], [1, 2, 3, 4]]
output =[]
total = 0
for row in data:
  for val in row[0:len(row)]:
   total += val
output.append(total)
print(output)

However, the results of this program is [6, 8, 18]. Any help would be appreciated.

Answer 1

Use a list comprehension .

Each element in list is iterable , this fact makes sum the best option for this task.

>>> data = [[1,2,3], [2], [1, 2, 3, 4]]
>>> [sum(d) for d in data]
[6, 2, 10]

Now, if you want to know what was your problem...

Place the accumulator after the data loop, and feed the list after every row loop:

>>> data = [[1,2,3], [2], [1, 2, 3, 4]]
>>> output = []
>>> for row in data:
...     total = 0
...     for val in row[0:len(row)]:
...         total += val
...     output.append(total)
...
>>> output
[6, 2, 10]

Answer 2

Use map() :

data = [[1,2,3], [2], [1, 2, 3, 4]] 
print(list(map(sum, data)))
# [6, 2, 10]

Or list-comprehension:

data = [[1,2,3], [2], [1, 2, 3, 4]]
print([sum(x) for x in data])
# [6, 2, 10]