# 21 Number game in Python

• Difficulty Level : Hard
• Last Updated : 31 Jan, 2022

21, Bagram, or Twenty plus one is a game which progresses by counting up 1 to 21, with the player who calls “21” is eliminated. It can be played between any number of players.

Implementation
This is a simple 21 number game using Python programming language. The game illustrated here is between the player and the computer. There can be many variations in the game.

• The player can choose to start first or second.
• The list of numbers is shown before the Player takes his turn so that it becomes convenient.
• If consecutive numbers are not given in input then the player is automatically disqualified.
• The player loses if he gets the chance to call 21 and wins otherwise.

Winning against the computer can be possible by choosing to play second. The strategy is to call numbers till the multiple of 4 which would eventually lead to 21 on computer hence making the player the winner.

 `# Python code to play 21 Number game`` ` `# returns the nearest multiple to 4``def` `nearestMultiple(num):``    ``if` `num >``=` `4``:``        ``near ``=` `num ``+` `(``4` `-` `(num ``%` `4``))``    ``else``:``        ``near ``=` `4``    ``return` `near`` ` `def` `lose1():``    ``print` `(``"\n\nYOU LOSE !"``)``    ``print``(``"Better luck next time !"``)``    ``exit(``0``)``     ` `# checks whether the numbers are consecutive``def` `check(xyz):``    ``i ``=` `1``    ``while` `i<``len``(xyz):``        ``if` `(xyz[i]``-``xyz[i``-``1``])!``=` `1``:``            ``return` `False``        ``i ``=` `i ``+` `1``    ``return` `True`` ` `# starts the game``def` `start1():``    ``xyz ``=` `[]``    ``last ``=` `0``    ``while` `True``:``        ``print` `(``"Enter 'F' to take the first chance."``)``        ``print``(``"Enter 'S' to take the second chance."``)``        ``chance ``=` `input``(``'> '``)``         ` `        ``# player takes the first chance``        ``if` `chance ``=``=` `"F"``:``            ``while` `True``:``                ``if` `last ``=``=` `20``:``                    ``lose1()``                ``else``:``                    ``print` `(``"\nYour Turn."``)``                    ``print` `(``"\nHow many numbers do you wish to enter?"``)``                    ``inp ``=` `int``(``input``(``'> '``))``                     ` `                    ``if` `inp > ``0` `and` `inp <``=` `3``:``                        ``comp ``=` `4` `-` `inp``                    ``else``:``                        ``print` `(``"Wrong input. You are disqualified from the game."``)``                        ``lose1()``             ` `                    ``i, j ``=` `1``, ``1`` ` `                    ``print` `(``"Now enter the values"``)``                    ``while` `i <``=` `inp:``                        ``a ``=` `input``(``'> '``)``                        ``a ``=` `int``(a)``                        ``xyz.append(a)``                        ``i ``=` `i ``+` `1``                     ` `                    ``# store the last element of xyz.``                    ``last ``=` `xyz[``-``1``] ``                     ` `                    ``# checks whether the input ``                    ``# numbers are consecutive``                    ``if` `check(xyz) ``=``=` `True``: ``                        ``if` `last ``=``=` `21``:``                            ``lose1()``                             ` `                        ``else``:``                            ``#"Computer's turn."``                            ``while` `j <``=` `comp:``                                ``xyz.append(last ``+` `j)``                                ``j ``=` `j ``+` `1``                            ``print` `(``"Order of inputs after computer's turn is: "``)``                            ``print` `(xyz)``                            ``last ``=` `xyz[``-``1``]``                    ``else``:``                        ``print` `(``"\nYou did not input consecutive integers."``)``                        ``lose1()``                         ` `        ``# player takes the second chance``        ``elif` `chance ``=``=` `"S"``:``            ``comp ``=` `1``            ``last ``=` `0``            ``while` `last < ``20``:``                ``#"Computer's turn"``                ``j ``=` `1``                ``while` `j <``=` `comp:``                    ``xyz.append(last ``+` `j)``                    ``j ``=` `j ``+` `1``                ``print` `(``"Order of inputs after computer's turn is:"``)``                ``print` `(xyz)``                ``if` `xyz[``-``1``] ``=``=` `20``:``                    ``lose1()``                     ` `                ``else``:``                    ``print` `(``"\nYour turn."``)``                    ``print` `(``"\nHow many numbers do you wish to enter?"``)``                    ``inp ``=` `input``(``'> '``)``                    ``inp ``=` `int``(inp)``                    ``i ``=` `1``                    ``print` `(``"Enter your values"``)``                    ``while` `i <``=` `inp:``                        ``xyz.append(``int``(``input``(``'> '``)))``                        ``i ``=` `i ``+` `1``                    ``last ``=` `xyz[``-``1``]``                    ``if` `check(xyz) ``=``=` `True``:``                        ``# print (xyz)``                        ``near ``=` `nearestMultiple(last)``                        ``comp ``=` `near ``-` `last``                        ``if` `comp ``=``=` `4``:``                            ``comp ``=` `3``                        ``else``:``                            ``comp ``=` `comp``                    ``else``:``                        ``# if inputs are not consecutive``                        ``# automatically disqualified``                        ``print` `(``"\nYou did not input consecutive integers."``)``                        ``# print ("You are disqualified from the game.")``                        ``lose1()``            ``print` `(``"\n\nCONGRATULATIONS !!!"``)``            ``print` `(``"YOU WON !"``)``            ``exit(``0``)``             ` `        ``else``:``            ``print` `(``"wrong choice"``)``                         ` `         ` `game ``=` `True`    `while` `game ``=``=` `True``:``        ``print` `(``"Player 2 is Computer."``)``        ``print``(``"Do you want to play the 21 number game? (Yes / No)"``)``        ``ans ``=` `input``(``'> '``)``        ``if` `ans ``=``=``'Yes'``:``            ``start1()``        ``else``:``            ``print` `(``"Do you want quit the game?(yes / no)"``)``            ``nex ``=` `input``(``'> '``)``            ``if` `nex ``=``=` `"yes"``:``                ``print` `(``"You are quitting the game..."``)``                ``exit(``0``)``            ``elif` `nex ``=``=` `"no"``:``                ``print` `(``"Continuing..."``)``            ``else``:``                ``print` `(``"Wrong choice"``)``                `

Output:

```Player 2 is Computer.
Do you want to start the game? (Yes/No)
> Yes
Enter 'F' to take the first chance.
Enter 'S' to take the second chance.
> S
Order of inputs after computer's turn is:
[1]

How many numbers do you wish to enter?
> 3
> 2
> 3
> 4
Order of inputs after computer's turn is:
[1, 2, 3, 4, 5, 6, 7]

How many numbers do you wish to enter?
> 1
> 8
Order of inputs after computer's turn is:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

How many numbers do you wish to enter?
> 1
> 12
Order of inputs after computer's turn is:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

How many numbers do you wish to enter?
> 1
> 16
Order of inputs after computer's turn is:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

How many numbers do you wish to enter?
> 1
> 20

CONGRATULATIONS!!!
YOU WON!
```

Try it yourself as exercise:

• You can further enhance program by increasing the number of players.
• You can also use only even/odd numbers.
• You can replace the numbers with binary number system.
• You can add levels with variations in the game.

My Personal Notes arrow_drop_up