8Queens.py

class Queens:
     def __init__(self, size):
         self.size = size
         self.solutions = 0
         self.solve()
 
     def solve(self):
         positions = [-1] * self.size
         self.put_queen(positions, 0)
         print("Found", self.solutions, "solutions.")
 
     def put_queen(self, positions, target_row):
         if target_row == self.size:
             self.show_full_board(positions)
             self.solutions += 1
         else:
             for column in range(self.size):
                 if self.check_place(positions, target_row, column):
                     positions[target_row] = column
                     self.put_queen(positions, target_row + 1)
 
     def check_place(self, positions, ocuppied_rows, column):
         for i in range(ocuppied_rows):
             if positions[i] == column or \
                 positions[i] - i == column - ocuppied_rows or \
                 positions[i] + i == column + ocuppied_rows:
 
                 return False
         return True
 
     def show_full_board(self, positions):
         for row in range(self.size):
             line = ""
             for column in range(self.size):
                 if positions[row] == column:
                     line += "Q "
                 else:
                     line += ". "
             print(line)
         print("\n")        

if __name__ == "__main__":
    n=int(input("enter no of queens"))
    Queens(n)