Tag Archives: iterative development

Creating a dice game in Python (part 2)

Iteration 2

In the second iteration of the development of Seven Out we add an outer loop so that the game will continue until the player’s total score equals or exceeds the target score – in this case 200. In the pseudocode shown below the outer loop is modelled as a while loop with a condition to check whether the target score has been met. The algorithm used inside of the outer loop is the same as that used in iteration 1 except a new variable is used to keep track of the score for the current round.


set target to 200
set score to 0
while score < target
   set round_score to 0
   loop
      set total to sum of two random integers between 1 and 6
      if total = 7
      then
         exit loop
      else
         add total to round_score
      end if
    end loop
    output round_score
end while
output score

The code written for this iteration is similar to that from iteration 1. New lines of code are highlighted in the listing below. Line 6 contains a while loop with a condition that checks that the score is less than the target. The while loop will continue while
this condition is true. In particular this while loop will always run at least once. Line 7 creates a new variable to represent the score for the current round - the value for this variable is reset to zero each time the outer loop is repeated. Line 17 updates the round score by adding the current dice total. Note that when a total of 7 is rolled this is not added to the round score.

import random

target = 200
score = 0

while score < target:
    round_score = 0
    valid = True
    while valid:
        roll1 = random.randint(1, 6)
        roll2 = random.randint(1, 6)
        total = roll1 + roll2
        if total == 7:
            valid = False
            print(total)
        else:
            round_score = round_score + total
            print(total, end=", ")
    score = score + round_score
    print("You scored", round_score, "this round")
    print("Total score is", score)

print("Well done. You got to", target)

Line 18 of the code uses an option within the print statement to alter its behaviour. The end option will by default print a newline character at the end of the output, meaning that subsequent output will appear on a new line. In this case we replace the default behaviour and instead end with a comma followed by a space. This means all of the totals for a round will be printed out on one line.

Output generated by running the game is shown below. For each round a list of comma-separated dice totals are shown, followed by the total for that round and then the total score. At the end of the game the player's total is shown. 

8, 2, 3, 8, 2, 4, 9, 7
You scored 36 this round
Total score is 36
9, 5, 8, 10, 7
You scored 32 this round
Total score is 68
7
You scored 0 this round
Total score is 68
2, 9, 5, 11, 4, 4, 10, 6, 11, 11, 3, 4, 7
You scored 80 this round
Total score is 148
3, 6, 9, 7
You scored 18 this round
Total score is 166
6, 5, 5, 4, 7
You scored 20 this round
Total score is 186
8, 6, 4, 3, 6, 6, 7
You scored 33 this round
Total score is 219
Well done. You got to 200

Creating a dice game in Python (part 1)

Introduction

In this series of posts we will look at how to code a simple dice game in Python, starting with the initial concept, all the way through to the coding and adding extension features.


The game that we will develop is a simple two dice game called Sevens out. The game rules from lovetoknow.com are as follows:

Game rules

  1. The players decide upon a winning score, this could be 500 or 1,000.
  2. Each player, in turn, throws the dice.
  3. Each player rolls and continues to roll the dice until they throw a 7.
  4. They score the sum of all the numbers thrown before the 7.
  5. Players announce their tally after each throw and once they have thrown a 7, their score is noted on the score sheet.
  6. Doubles score double the value. For example, if a player who throws two 4s making eight, their score is 16.
  7. The player reaches the pre-arranged total first is the winner.

Iteration 1

Rather than attempting to develop the entire game in one pass, we will develop the game in multiple stages using an iterative development approach.
For the first iteration we will get one round of dice rolling completed for a single player.

Before writing any code we will develop a high-level design using pseudocode. This allows us to consider the key logical parts of the algorithmic solution without having to get bogged downed in the finer details of exactly how to code this in Python.

The pseudocode for our proposed first iteration is shown below. The most important part of the pseudocode is that it conveys the intended logic of the problem we are solving. For example the third and fourth lines of pseudocode indicates that a random number between 1 and 6 needs to be generated. How this is done does not matter at this stage – indeed the solution is dependent on the coding language being used, whereas pseudocode should be coding language independent.


set score to 0
loop
   set roll1 to random number between 1 and 6
   set roll2 to random number between 1 and 6
   set total to roll1 + roll2
   if total = 7
   then
      exit the loop
   else
      set score to score + total
   end if
end loop
output score

The resulting code in Python is almost a line for line translation of the pseudocode. One noteworthy change is the addition of a Boolean-valued variable, valid, which is used to indicate whether all rolls to date are valid (do not add up to 7). The while loop will continue whilst this variable is true. When a total of 7 is rolled the value of the variable becomes false. The use of this loop termination variable is highlighted in the code below. The relationship between the remainder of the code and the pseudocode should hopefully be evident.

import random

valid = True
score = 0

while valid:
    roll1 = random.randint(1, 6)
    roll2 = random.randint(1, 6)
    total = roll1 + roll2
    if total == 7:
        valid = False
    else:
        score = score + total

print("Score is", score)

The screenshot below shows the code running in the Pycharm IDE. The code runs until a total of 7 is rolled and then prints the resulting score.