Why is my for loop only printing the first if statement repeatedly?

Question

I am trying to create a list representing a chess board. I have this code for it:

#possible list items
EMPTY = "-"
ROOK = "ROOK"
KNIGHT = "KNIGHT"
BISHOP = "BISHOP"
QUEEN = "QUEEN"
KING = "KING"
PAWN = "PAWN"
board = []

royal_row = [] #list for row containing king

pawn_row = []#list for pawn row

row = [] #generic row

#setting the board
for i in range(8):
    if i == 0 or 7:
        royal_row = [ROOK,KNIGHT,BISHOP,QUEEN,KING,BISHOP,KNIGHT,ROOK]
        board.append(royal_row)
        
    elif i == 1 or 6:
        pawn_row = [PAWN for i in range(8)]
        board.append(pawn_row)
        
    else: 
        row = [EMPTY for i in range(8)]
        board.append(row)

for i in range(8):
    print(board[i], end = "\n")

When I run this code it just prints:

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

my expected output is:

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

['PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN']

['-', '-', '-', '-', '-', '-', '-', '-']

['-', '-', '-', '-', '-', '-', '-', '-']

['-', '-', '-', '-', '-', '-', '-', '-']

['-', '-', '-', '-', '-', '-', '-', '-']

['PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN', 'PAWN']

['ROOK', 'KNIGHT', 'BISHOP', 'QUEEN', 'KING', 'BISHOP', 'KNIGHT', 'ROOK']

If I separate the 1, 0, 6, and 7 to their own elif clause then it prints correctly but I want to understand why the original code doesn't

use in: `if i in [0,7]:` – It_is_Chris Aug 27 '21 at 19:50 — It_is_Chris, Aug 27 '21 at 19:50

HPringles · Answer 1 · 2021-08-27T19:53:00.327

0

if i == 0 or 7:

This statement is essentially the below

if i == 0 or 7 != 0

So, because 7 is always greater than 1, it is always true.

To fix this, try the following instead

if i == 1 or i == 7

edited Aug 27 '21 at 19:53

answered Aug 27 '21 at 19:44

HPringles

1,042
6
15

The use of `or 7` is not equivalent to `or 7 >=1`. – jarmod Aug 27 '21 at 19:48
Oops, you're right. It's just non-zero isn't it. My bad – HPringles Aug 27 '21 at 19:50
It's not `or 7 != 1` either. – jarmod Aug 27 '21 at 19:51
Yeah sorry, changed the >= but not the number. That's right now, right? – HPringles Aug 27 '21 at 19:53
1

Yup, it's good now. – jarmod Aug 27 '21 at 19:53

score 0 · Accepted Answer · answered Aug 27 '21 at 19:46

You decide to change in the if's and put: i == 0 or i == 7 and i == 1 or i == 6

#possible list items
EMPTY = "-"
ROOK = "ROOK"
KNIGHT = "KNIGHT"
BISHOP = "BISHOP"
QUEEN = "QUEEN"
KING = "KING"
PAWN = "PAWN"
board = []

royal_row = [] #list for row containing king

pawn_row = []#list for pawn row

row = [] #generic row

#setting the board
for i in range(8):
    if i == 0 or i == 7:
        royal_row = [ROOK,KNIGHT,BISHOP,QUEEN,KING,BISHOP,KNIGHT,ROOK]
        board.append(royal_row)

    elif i == 1 or i == 6:
        pawn_row = [PAWN for i in range(8)]
        board.append(pawn_row)

    else:
        row = [EMPTY for i in range(8)]
        board.append(row)

for i in range(8):
    print(board[i], end = "\n")

Thanks !I did that and it fixed the issue. Do you know why writing it the way I originally did would cause that line to repeat itself? — Binomial_Gnome, Aug 27 '21 at 19:56
@Binomial_Gnome I wrote it at the beginning. before the code. When you did the if you didn't put equality for both numbers. You have to do: `if i == 0 or i == 7` and also `elif i == 1 or i == 6` — Piero, Aug 27 '21 at 20:00

Why is my for loop only printing the first if statement repeatedly?

2 Answers2