Game Development Reference
In-Depth Information
Letting the Player Enter Their Move
75. def getPlayerMove(board):
76. # Let the player type in his move.
77. move = ' '
78. while move not in '1 2 3 4 5 6 7 8 9'.split() or not
isSpaceFree(board, int(move)):
79. print('What is your next move? (1-9)')
80. move = input()
81. return int(move)
The
getPlayerMove()
function asks the player to enter the number for the space
they wish to move. The function makes sure that they enter a space that is a valid space (an
integer 1 through 9). It also checks that the space that is not already taken, given the Tic
Tac Toe board passed to the function in the
board
parameter.
The two lines of code inside the
while
loop simply ask the player to enter a number
from 1 to 9. The loop's condition will keep looping, that is, it will keep asking the player
for a space, as long as the condition is
True
. The condition is
True
if either of the
expressions on the
left
or
right
side of the
or
keyword is
True
.
The expression on the
left
side checks if the move that the player entered is equal to
'1'
,
'2'
,
'3'
, and so on up to
'9'
by creating a list with these strings (with the
split()
method) and checking if move is in this list.
'1 2 3 4 5 6 7 8 9'.split()
evaluates to be the same as
['1', '2', '3', '4', '5', '6', '7', '8',
'9']
, but it easier to type.
The expression on the
right
side checks if the move that the player entered is a free space
on the board. It checks this by calling the
isSpaceFree()
function we just wrote.
Remember that
isSpaceFree()
will return
True
if the move we pass is available on
the board. Note that
isSpaceFree()
expects an integer for
move
, so we use the
int()
function to evaluate an integer form of
move
.
We add the
not
operators to both sides so that the condition will be
True
when both of
these requirements are unfulfilled. This will cause the loop to ask the player again and
again until they enter a proper move.
Finally, on line 81, we will return the integer form of whatever move the player entered.
Remember that
input()
returns a string, so we will want to use the
int()
function to
evaluate the string as an integer.
Short-Circuit Evaluation
You may have noticed there is a possible problem in our
getPlayerMove()
function.
What if the player typed in
'X'
or some other non-integer string? The
move not in
