Python: map, zip, input, sum
N, X = map(int, input().split()) maps two space-separated integers which represent the total number of students and total number of subjects. So, 5 3 indicates that five students participated in three subjects. In this case, N, X becomes 5, 3.
marks = [] stores space-separated grade point values, e.g. 89 90 94 88 95. marks.append(map(float, input().split())) is then used to append grade point values to the empty marks list, which loops three times, according to the value assigned to X, which is 3.
Finally, the second for loop, iterates through each row. Dividing the sum total of each column by the length of each column.
if __name__ == '__main__': indicates that the script above will run only as a __main__ or stand-alone program. In other words: only when it is directly executed. So the script above can not be imported into another program as a module, e.g. import map_zip_grades.
