''' Purpose: stepping stone to nested looping
'''

# get number of rows and columns
reply = input( 'Number of rows and columns: ' )

srows, scols = reply.split()
# we need to convert into ints here because input() returns string!
nrows = int( srows )
ncols = int( scols )

# nested for loops! PLZ REVIEW THIS
# you can have a for loop in another for loop

# produce nrows rows of output
#    for each row produce ncols columns of output
#           row r's c-th output, is value of r + c

# for each row in the range 0 (inclusive) to nrows (exclusive)
# r includes 0 and goes up to but not including nrows --> [0, 1, 2, ... nrows-1]
for r in range( 0, nrows ):
    print( 'row', r, ':' )
    # PLZ MAKE SURE YOU UNDERSTAND THIS - ask if you're confused :)
    # for each row, we process EACH COLUMN
    # this inner for loop will run to COMPLETION before the outer for loop starts on ITS next iteration
    # then this inner for loop will run to completion again for the next outer loop
    # and so on until the outer for loop finishes!!!
    # this for loop occurs for each of the for r loop! runs to completion!
    for c in range( 0, ncols ):
        # print( 'r =', r, 'c =', c )
        # print( '   ', c, end=' ' )           # if we add end=, then we print each column number on the same line
                                               # for each row

        # determine cell value for column c
        cell = r + c

        # print cell value
        print(cell, end="\t")

        # if nrows = 2, ncols = 3
        # r = 0
            # c = 0
            # cell = 0 + 0 = 0

            # c = 1
            # cell = 0 + 1 = 1

            # c = 2
            # cell = 0 + 2 = 3

        # r = 1     -- outer loop starts its next iteration (the next value)
            # c = 0 -- inner loop starts over again
            # cell = 1 + 0 = 1

            # c = 1
            # cell = 1 + 1 = 2

            # c = 2
            # cell = 1 + 2 = 3
        # since r = 2, the outer for loop finishes and the code exits

    # reaches this point when the inner for loop finishes BUT STILL IN THE OUTER FOR LOOP
    print() # this will end the current line then so the next row will print on a new line

# to comment several lines at the same time --> highlight them --> cntrl/command + forward slash key