Going from a for loop to a list comprehension

Question

I have a program that displays and inventory report and i was just wondering how I could put the following into a list comprehension instead of a for-loop...I'm kind of a noob at all this python jargon but from what i know is that anything that is in the form of a for-loop can also be expressed as a list comprehension....ANY help would be appreciated

def rowSum(TotSize,data,row,col):
    """Calculates the sum of each row in a given 2 dimensional list and stores
it into a given one dimensional list"""
    for i in range(row):
        sum = 0
        for j in range(col):
            sum += data[i][j]
        TotSize[i] = sum

Answer 1

Your code is essentially equivalent to

TotSize[:] = map(sum, data)

This will sum over all of data, not only the first row rows and the firs col cols. It will also resize TotSize to match the number of rows data has (assuming TotSize is a list).

I wonder why you are passing in the list that should store the result. In Python, you'd usually simply return that list:

def row_sums(data):
    return map(sum, data)

Now it's questionable whether it's worthwhile to define a function for this at all…

Answer 2

I might have misunderstood your question, but are you asking for something like this?

>>> testdata = [[5, 6, 8], [], range(8), [42]]
>>> ToTSize = [sum(row) for row in testdata]
>>> ToTSize
[19, 0, 28, 42]