How is this possible ?? can someone explain this?

Question

iam making easy battleship game. but there is something that doesnt make sense for me. when there is strictly append in the first loop it has different output than if i wrote the same thing with variable..

import random

BOARD = []

for i in range(5):
    BOARD.append(["O"]*5)

x = random.randint(1,5)
y = random.randint(1,5)

while True:
    for i in BOARD:
        print(" ".join(i))

    row = int(input(": "))
    column = int(input(": "))

    if x == row and y == column:
        print("you win")
    else:
        BOARD[x - 1][y - 1] = "X"

in case of miss there is output like this

O O O O O
O X O O O
O O O O O
O O O O O
O O O O O

but if i wrote this code.. which is similar to previous.. only difference is a variable in the first loop... it has totaly different output..

import random

BOARD = []

Q = ["O"]*5

for i in range(5):
    BOARD.append(Q)

x = random.randint(1,5)
y = random.randint(1,5)

while True:
    for i in BOARD:
        print(" ".join(i))

    row = int(input(": "))
    column = int(input(": "))

    if x == row and y == column:
        print("you win")
    else:
        BOARD[x - 1][y - 1] = "X"

but there is output like this.. it doesnt make sense for me

O x O O O
O X O O O
O x O O O
O x O O O
O x O O O

is there on this site anyone who can explain this ??? nobody can help

Here `BOARD` contains a list with **references to the same list**. So if you modify `BOARD[0]` then the update is reflected in `BOARD[1]`... — Willem Van Onsem, Feb 17 '17 at 10:42
You are marking the `X` based on `x` and `y` which are randomly chosen... — José Sánchez, Feb 17 '17 at 10:42
Please give some useful information in the title, or we have to vote down this question. — Musen, Feb 17 '17 at 10:46

score 1 · Answer 1 · answered Feb 17 '17 at 10:55

This must solve the issue:

import random

BOARD = []

Q = ["O"]*5

for i in range(5):
    BOARD.append(list(Q))

x = random.randint(1,5)
y = random.randint(1,5)

while True:
    for i in BOARD:
        print(" ".join(i))

    row = int(input(": "))
    column = int(input(": "))

    if x == row and y == column:
        print("you win")
    else:
        BOARD[x - 1][y - 1] = "X"

You must make copy of the list Q: BOARD.append(list(Q))

How is this possible ?? can someone explain this?

1 Answers1