SIMPLE TIC-TAC-TOE GAME - LEARNING TO CODE WITH PYTHON Ep 7

abmakko(62)

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Hello friends, this is a blog about my programming journey, I am basically teaching myself how to code. This is a formal documentation about my progress.

Today we're going to learn about dictionaries and use them to create a basic shell game in python. From the name dictionary, it is a bit self-explanatory. dictionaries consist of words which have meanings. In python, we can create our own custom dictionary, but in python, there is a simple twist, the words are called keys, and the meanings are called values.

In order to know the syntax for creating dictionaries, let us create a simple dictionary called diet, it will contain what we'll have for breakfast, lunch and dinner.

diet = {'breakfast':'eggs and bread' , 
         'lunch' : 'rice and chicken', 
         'dinner' : 'steak and wine'}

The dictionary titled "diet" consists of words(keys) and meanings(values), the keys are (breakfast, lunch, rice), the values of the respective keys are the strings (egg and bread, rice and chicken, steak and wine)

All these data can be stored and edited during program run. for example the dictionary can be edited as follows.

diet[breakfast] = 'beef and noodles'

This single line above can change the breakfast value from "eggs and bread" to "beef and noodles"

diet[lunch] = 'nothing'

This line can also change the value inside the lunch key... following the same syntax we can edit the dictionary as we please.

In order to display the content of our dictionaries, we can just use the print function.

print(diet)

This line of code below can be used to display the values stored in the key-breakfast.

print(diet[breakfast])

There are other methods you can also use to manipulate dictionaries but for the purpose of our basic game, this is the method we'll need.

Create a simple tic-tac-toe game in python

First we will create the dictionary titled "theBoard", this is basically a dictionary that assigns values to the 9 nodes in our tic-tac-toe game. I titled the node from 1-9, each node represents the 9 positions on our game board

theBoard = {'7': ' ', '8': ' ', '9': ' ',
              '4': ' ', '5': ' ', '6': ' ',
              '1': ' ', '2': ' ', '3': ' '}

Each node-position is a key in our dictionary and the values (X or O) can be stored in any of those keys. I illustrated the numbered node below, we are following this simple grid representation.

But the values stored in those numbered-nodes are empty at the moment.

Next, we will define(def) a function titled "display_board" which displays the game board. It basically consists of print statements that prints each value in the dictionary and spacing them by putting dashes and space-tabs in-between.

def display_board(theBoard):    
        print('  ', theBoard['7'], '  |','  ' ,theBoard['8'], '  |', '  ',theBoard['9'])
        print('-------+--------+--------')
        print('  ', theBoard['4'], '  |','  ' ,theBoard['5'], '  |', '  ',theBoard['6'])
        print('-------+--------+--------')
        print('  ', theBoard['1'], '  |','  ' ,theBoard['2'], '  |', '  ',theBoard['3'], '\n')

Each time we call the function above, it displays the values in our dictionary, similar to this.

Next we will define(def) another function(titled "instruction") that print some instructions to the user, It consists of print statements that instructs the user on what keys to press on the keyboard to place the (X or O)

  def instruction():
         print("press the numbers to place your X or O in position\n")    
         print('  ', '7', '  |','  ' ,'8', '  |', '  ','9')
         print('-------+--------+--------')
         print('  ', '4', '  |','  ' ,'5', '  |', '  ','6')
         print('-------+--------+--------')
         print('  ', '1', '  |','  ' ,'2', '  |', '  ','3', '\n')
         print('=========================\n')

If we run this function above it displays a prompt like this.

Now we'll get to the real meat of the program, we'll define a function(check_winner) that checks the value of each keys in our dictionary, if any 3 (X or O) forms a straight line a winner is found. we will create several if statements which checks each numbered keys(in 3 groups) that are equal to each other meaning they are in a straight line, for example the keys(7, 4 and 1) are in a straight line. we will repeat the same pattern for all the win outcomes.

 def check_winner(theBoard):
       check = 0    
       if theBoard['7'] == theBoard['8'] == theBoard['9'] != ' ' :
           check = 1
       elif theBoard['7'] == theBoard['4'] == theBoard['1'] != ' ':
           check = 1
       elif theBoard['7'] == theBoard['5'] == theBoard['3'] != ' ':
           check = 1
       elif theBoard['4'] == theBoard['5'] == theBoard['6'] != ' ': 
           check = 1
       elif theBoard['1'] == theBoard['2'] == theBoard['3'] != ' ':
           check = 1
       elif theBoard['1'] == theBoard['5'] == theBoard['9'] != ' ':
          check = 1
      elif theBoard['9'] == theBoard['6'] == theBoard['3'] != ' ':
           check = 1
       elif theBoard['2'] == theBoard['5'] == theBoard['8'] != ' ':
           check = 1
       return check

Each if-statements and consecutive elif-statements in the code above uses the mathematical python syntax which check if 3-straigh-line nodes are equal(==) to each other and are not empty (!=' ').

Also the logic behind this function is to use a basic check method. the variable (check) is given a default value of 0 but if any if-statement is true, check is changed to 1. at the end of the function the value of check is returned. if check is 0 then there is no winner but if check is equal to 1 then a winner has been found.

We'll now define our final function(titled "play"), play will basically consist of our game play codes which will change the turns of each player, call on the other previously defined functions, and also confirm our winner, I will try to explain each line of the code below. The explanation would be lengthy but I must break it down for my further understanding and yours.

 def play(theBoard):
    node = "X"
    for i in range(9):
        instruction()
        display_board(theBoard)
        print('it is ', node, 'turn to play \n')
        turn = input()
         while True:
            if theBoard[turn] == ' ':
                theBoard[turn] = node
                break
            else:
                print("you've already played that move, place your", node, "elsewhere\n")
                instruction()
                display_board(theBoard)
                turn = input()
        check = check_winner(theBoard)
        if check == 1:
            print('The winner is', node)
            break
        else:
            print("No winner, play again?")
        if node == 'X':
            node = 'O'
        else:
            node = 'X'

line 2

At the beginning of the "play" function. The node will be equal to X meaning the first player will use the first-X-node. This node will be changing between X and O several times in the program.

line 3

A basic for loop is initated to run 9-times because the both players gets a total of 9 turns in the game, there are only 9 positions to the played.

line 4

Inside the for loop, we will first call the instruction() and display_board(theBoard) function which were defined earlier in the code. the purpose of these function is to display the instruction and the current-game-board within the 9-times-loop. the game board will keep displaying and updating throughout the game play.

line 5

Next is a simple print-statement(display prompt that shows the current player-node) followed by an input function that accepts the numbered-keys between(1-9) from the user and stored in the variable(turn), each of these numbers have a positional value in our dictionary-grid as explained earlier.

line 8

When one of the players fufil his/her turn and stores an(X or O) value in the dictionary. we do not want another user to override his play and input into a filled spot. so we will create an infinite loop with the (while True) statement. infinite loops are used when we are uncertain about the number of times or loops a user would perform a task. since we do not know how many times the user would make this mistake, this infinite loop would contain a condition that would break out of the loop when the user performs the right task- putting the(X or O) into an empty spot.

line 9

Inside the while True infinite loop, it contains an If-statement which checks if the position on the board is empty. If it is empty it stores the X-node into the postition(turn) entered by the user, and breaks out of the loop in the next line.

line 12

Another provision is made in form of an else-statement. if the position is already filled, the else-statement-code block is activated, it instruct the user about the mistake, displays the current board with the pre-defined functionss and accept a new input for the variable(turn), the variable will keep testing against the dictionary in the infinite-loop, if the the dictionary-position is occupied the loop will keep running.

line 17

The predefined check_winner function is called and checks for the winner. the value(1 or 0) returned from the function is stored in the variable(check).

line 18

The if statement checks if the returned value is 1. if (check = 1) then it runs the if-code-block which declares the winner and breaks out of the 9-times for-loop in line 3. If the value of check is not 1, the else-statement is activated- which declares the there is no winner.