How can I sum a column of a list?

Question

I have a Python array, like so:

[[1,2,3],
 [1,2,3]]

I can add the row by doing sum(array[i]), how can I sum a column, using a

Answer 1

[sum(row[i] for row in array) for i in range(len(array[0]))]

That should do it. len(array[0]) is the number of columns, so i iterates through those. The generator expression row[i] for row in array goes through all of the rows and selects a single column, for each column number.