python - exec function not working properly in python 3.6

Question

Code I wrote

tile1=0; player1=1; turn=player1

def s():
   global tile1,turn,player1
   print("Before",tile1)
   string='tile' + '1' # I am getting 1 by some function that's why I need to create variable string                                     
   exec("%s=%d" %(string,turn))
   print("After",tile1)  
s()

Output what I expected
Before 0
After 1

Output what i got
Before 0
After 0

If I write the code without the function , it gives the expected output

tile1=0; player1=1; turn=player1
print("Before",tile1)
string='tile' + '1'                                  
exec("%s=%d" %(string,turn))
print("After",tile1)

I want to ask how to correct this code so that I get the expected output. Also, I am not allowed to use list and dictionary.