Populating cells within a 2d list in python

Question

Exact wording from assignment: We pass in 2 numbers, A and B. You should create a list with A rows and B columns. You should then populate each cell like this … 'R0C0', 'R0C1', 'R0C2' etc. I was able to create the list with all 0's but not able to modify to correct output.

Was given this but don't know how to implement.

for row in rows:  # Each row
  for col in cols:  # The columns on the current row
      print('This is row: %s and col: %s' % (row,col)


    A= int(sys.argv[1])
    B= int(sys.argv[2])

    # Your code goes here
    a = [([0]*B) for row in range(0 , A)]

    print(a)

Expected Output: [['R0C0', 'R0C1', 'R0C2'], ['R1C0', 'R1C1', 'R1C2']] Your Program Output: [[0, 0, 0], [0, 0, 0]]

Answer 1

You're not using either A nor B in your result, you're using 0 , that's why you're getting [[0, 0, 0], [0, 0, 0], [0, 0, 0]] .

You can fix that by using string formatting to get the row and column you want.

num_rows = int(sys.argv[1])
num_columns = int(sys.argv[2])

result = [["R{row}C{col}".format(row=row, col=col) for col in range(num_columns)] for row in range(num_rows)]

Or, more succinctly (with f-strings in Py3.6+):

result = [[f"R{row}C{col}" for col in range(num_columns)] for row in range(num_rows)]

You could also initialize your list, then iterate through and set each value, but I'm not sure what you gain from doing this in this example.

import itertools

def make_2d_list(self, rows, columns):
    """Makes a 2D list with None for each value."""

    return [[None for _ in range(columns)] for _ in range(rows)]

base_list = make_2d_list(num_rows, num_columns)

for row, col in itertools.product(range(num_rows), range(num_columns))
    # itertools.product is a concise form of nested for loops.
    # These two expressions are equivalent:
    #
    # for a, b, c, d, e in itertools.product(as, bs, cs, ds, es):
    #     ...
    #
    # for a in as:
    #     for b in bs:
    #         for c in cs:
    #             for d in ds:
    #                 for e in es:
    #                     ...
    base_list[row][col] = f"R{row}C{col}"