# Tic-Tac-Toe game in Python 3

I have written a code for a tic-tac-toe game and it works well. But, I don't know whether it is an efficient one. Any help on how to optimize it?

def restart():

num=[0 for i in range(9)]
board=[" " for i in range(9)]
a=2
start(board,a,num)

def wincheck(t):

for i in range(8):
if t[win[i][0]]==t[win[i][1]] and t[win[i][0]]==t[win[i][2]] and
t[win[i][1]]==t[win[i][2]] and t[win[i][0]]!=" ":
if t[win[i][0]]=="X":
print("Player 1 wins")
else:
print("Player 2 wins")
playa = input("Do you want to play again? Y/N")
if playa.lower() == "y":
restart()
else:
exit(0)
def display_board(t,a,num):

print( " "*3+'|'+" "*3+'|'+" "*3)
print("{0:^3}|{1:^3}|{2:^3}".format(t[6],t[7],t[8]))
print( " "*3+'|'+" "*3+'|'+" "*3)
print("-"*11)
print( " "*3+'|'+" "*3+'|'+" "*3)
print("{0:^3}|{1:^3}|{2:^3}".format(t[3],t[4],t[5]))
print( " "*3+'|'+" "*3+'|'+" "*3)
print("-"*11)
print( " "*3+'|'+" "*3+'|'+" "*3)
print("{0:^3}|{1:^3}|{2:^3}".format(t[0],t[1],t[2]))
print( " "*3+'|'+" "*3+'|'+" "*3)
wincheck(t)
if 0 not in num:
print("Draw")
restart()
start(t,a,num)

def start(board,a,num):

if a%2==0:
p1n=int(input("Player 1, Enter a number from 1 to 9"))
if p1n not in num:
num[p1n-1]=p1n
print(num)
else:
print("Please enter in a free space")
start(board,a,num)
board[p1n-1]="X"
a=a+1
display_board(board,a,num)
else:
p2n=int(input("Player 2, Enter a number from 1 to 9"))
if p2n not in num:
num[p2n-1]=p2n
print(num)
else:
print("Please enter in a free space")
start(board,a,num)
board[p2n-1]="O"
a=a+1
display_board(board,a,num)

a=2

board=[" " for i in range(9)]

num=[0 for i in range(9)]

win = [[0,1,2],[3,4,5],[6,7,8],[0,4,8],[6,4,2],[6,3,0],[7,4,1],[8,5,2]]

start(board,a,num)


Any help on how to optimize it?

Optimise readability, starting with following the Style Guide for Python Code.
(And yes, this is a useful step in optimising efficiency, too)

(The below reads an ill-tempered diatribe more than a code review, the sole exculpation being the explicit question in the title. (I should look for a well-receives SE resource bound to exist.))

How to write efficient source code for …?
Given a specification that looks ready for implementation,
- write tests shedding a light on correctness.
- fix(!) a limit for the effort to improve efficiency
- define a measure for efficient
(-if applicable, define relevant input data)
- automate measuring efficiency - memory usage is harder to assess than time used
(use available tools - timeit, for starters)
(It saves a lot of trouble to include (basic) functional tests here)
(Don't believe sub-second measurements.
Measure work completed in a fixed amount of time, not time used for a fixed amount of work.)
- use your first working version to establish a base line
- fix(!) what performance is good enough
- pick alternative implementations, jot down your guesses re. efficiency, measure
- time allowing (see limit above), experiment with improvements

I think your code is outstanding. I don't think you should be concerned about optimizing it since it runs quickly anyway. It is clear and easy to understand (which Python claims to be), so no need to obscure it with attempts to make it more "Pythonic".