11/19 can someone explain how/why this works?

#1
``````from random import randint

board = []

for x in range(0, 5):
board.append(["O"] * 5)

def print_board(board):
for row in board:
print " ".join(row)

print_board(board)

def random_row(board):
return randint(0, len(board) - 1)

def random_col(board):
return randint(0, len(board[0]) - 1)

ship_row = random_row(board)
ship_col = random_col(board)
guess_row = int(raw_input("Guess Row:"))
guess_col = int(raw_input("Guess Col:"))

print ship_row
print ship_col

if guess_row == ship_row and guess_col == ship_col:

print "Congratulations! You sank my battleship!"

else:

print "You missed my battleship!"
board[guess_row][guess_col] = "X"
print_board(board)``````

Why does:
board[guess_row][guess_col] = "X"
change the O to an X?

Thanks

#2

Why does:
board[guess_row][guess_col] = "X"
change the O to an X?

User input is saved in guess_row and guess_col, it could be that
guess_row == 3
guess_col == 4

So
`board[guess_row][guess_col] = "X"`
sets board[3][4] to "X"

Furthermore
`guess_row = raw_input("Guess Row:")`
prints "Guess Row:" to terminal and input is saved as a string to guess_row.

We need to have integers to index board so we cast string to int:
`guess_row = int(raw_input("Guess Row:"))`

#3

Okay that makes sense, thank you