Unwanted output in nested while-loop

Question

My prompt: "Write a program that uses two nested while loops to print off the rows and columns of a 3x3 grid (numbered 1 to 3), excluding the cells along the diagonal (i.e., where the row and column have the same value). The first three rows of your program's output should look like this:

1 2
1 3
2 1

I have coded it pretty well so far, but I am stuck with one extra unwanted output. How do I remove it?

row = 0
while row < 3:
    col = 0
    row += 1
    while col < 3:
        col += 1
        if row == col:
            col += 1
        print (row, col)

expected result should be:

but 3 4 is included as well.

Could you clarify what your input is? What I'm imagining this 3x3 grid to look like doesn't square with your expected output. — nmpauls
– nmpauls, Commented Sep 22, 2019 at 7:27
@nmpauls Hey, thanks for replying! I just want the coordinates as described in the post; minus the diagonals i.e 1 2, 1 3, 2 1, 2 3, 3 1, 3 2 — RoiMinuit
– RoiMinuit, Commented Sep 22, 2019 at 7:31

cs95 · Accepted Answer · 2019-09-22 07:30:20Z

1

Your if condition should change to print (i, j) only if they are not equal.

i = 1 
while i < 4:
    j = 1
    while j < 4:
        if i != j:
            print(i, j)
        j += 1
    i += 1
# 1 2
# 1 3
# 2 1
# 2 3
# 3 1
# 3 2

Also I've started iteration from 1 instead of 0 because this looks a little better organised to me.

P.S., the more idiomatic way of doing this would be using a list comprehension.

[(i, j) for i in range(1, 4) for j in range(1, 4) if i != j]
# [(1, 2), (1, 3), (2, 1), (2, 3), (3, 1), (3, 2)]

answered Sep 22, 2019 at 7:30

cs95

406k106 gold badges744 silver badges797 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

RoiMinuit Over a year ago

Thank you @cs95 I will definitely try this format as well!

Aryerez · Accepted Answer · 2019-09-22 07:31:43Z

0

It's because where row and col both equals to 3, you are increasing col to 4, and print. Modify to:

row = 0
while row < 3:
    col = 0
    row += 1
    while col < 3:
        col += 1
        if row != col:
            print (row, col)

answered Sep 22, 2019 at 7:31

Aryerez

3,5052 gold badges12 silver badges18 bronze badges

Collectives™ on Stack Overflow

Unwanted output in nested while-loop

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related