Replacing Values In Csv By Using Python

def update(all_marks, stud_num, mark, column, result): lines = [l for l in all_marks] for row in all_marks: if stud_num in row: lines[rows][column] = m

Solution 1:

Here is a modified version of your function that will return the output as expected:

def update(all_marks, stud_num, mark, column):
    for i in range(len(all_marks)):
        if stud_num in all_marks[i]:
            all_marks[i][column] = mark
    return all_marks

And here is how it works:

>>> marks
[['a', '', '', '', '', ''], ['b', '', '', '', '', ''], ['c', '', '', '', '', ''], ['d', '', '', '', '', ''], ['e', '', '', '', '', ''], ['f', '', '', '', '', ''], ['g', '', '', '', '', '']]

>>> update(marks,'a','10',2)
[['a', '', '10', '', '', ''], ['b', '', '', '', '', ''], ['c', '', '', '', '', ''], ['d', '', '', '', '', ''], ['e', '', '', '', '', ''], ['f', '', '', '', '', ''], ['g', '', '', '', '', '']]

Note that marks is now modified

>>> marks
[['a', '', '10', '', '', ''], ['b', '', '', '', '', ''], ['c', '', '', '', '', ''], ['d', '', '', '', '', ''], ['e', '', '', '', '', ''], ['f', '', '', '', '', ''], ['g', '', '', '', '', '']]

If you want to change that so that update simply returns a copy of modified data change the function in the following way:

def update(all_marks, stud_num, mark, column):
    tmp = all_marks
    for i in range(len(tmp)):
        if stud_num in tmp[i]:
            tmp[i][column] = mark
    return tmp

Solution 2:

Here is the working code:

def update(all_marks, stud_num, mark, column, result):
    lines = [l for l in all_marks]
    for row in range(len(all_marks)):
        if all_marks[row][0] == stud_num:
            lines[row][column] = mark

And here are the explanations:

for row in range(len(all_marks)):

=> you don't want to iterate over list objects (e.g. ['a','','','','','']) but over list indices

if stud_num == all_marks[row][0]:

=> This is to check only the first character of your row, not any character.

lines[row][column] = mark

=> typo here, should be row and not rows

Solution 3:

Looping on the row indices isn't as efficient as looping on the rows themselves. A more pythonic way would be

def update2(all_marks,stud_num,mark,column):
    for row in all_marks:
        if stud_num in row:
            row[column] = mark
    return all_marks