Haunted House – 3
Pattern recognition
The second stage of computational thinking is called pattern recognition. This involves finding patterns in data and making sense of data.
7. Data Structures
One thing to notice about the last solution is that it requires lots of ugly IF, THEN, ELSE statements, with some even nested inside others!
Your game only has 5 rooms; imagine if it had 100! There has to be a better way!
You need to make the game easy to extend, so more rooms doesn’t mean lots more code.
At this stage, you will begin using a data structure rather hard-coding lots of IF statements. Although your game won’t have any new features, it will be a lot easier to code.
Notice that once a room is linked to a direction, it leads to a room. So, you could describe your map that way.
If you linked those pairs, things will become a lot easier.
You have arrived at the second step of computational thinking.
Abstraction
Abstraction is the third stage computational thinking. Abstraction turns something complex into something simpler by removing detail and reducing it to a general principle or main idea.
8. Using Data Structures
A map of the house can be created using a data structure. Your ‘map’ will be created by pairing each room exit to a description of the connected room.
You can use a dictionary data structure for storing this pattern of paired items. A dictionary uses a keyword, known as a key, paired to a second word or string called its value. When you supply a keyword, the dictionary returns the matching value.
In Python, dictionaries are written using curly brackets {}, called braces. Let’s create a MAP for this game:
MAP = {
‘foyer_front’: ‘back door’,
‘foyer_right’: ‘lounge’,
‘foyer_back’: ‘front door’,
‘foyer_left’: ‘bedroom’,
‘bedroom_right’: ‘foyer’,
‘front_door_up’: ‘foyer’ }
The key is made up of three parts, which form a string:
name of the room + underscore + direction
To see if direction is legal, all you have to do is ask if the key is in the MAP dictionary using:
if key in MAP:
room = MAP[key]
The paired value names the connected room.
eg If you write MAP[‘foyer_front’], you get ‘back door’.
Notice, [ ] are to access dictionaries in Python.
* Create a second dictionary called DESC{} and pair room names with their descriptions.
* You also need a list data structure for items that will end the game. Note, list values in [ ].
FINNISH = [‘back door’, ‘lounge’, ‘quit’]
First you recognise a pattern in what you are doing with rooms in your game. Now you are representing these patterns with a dictionary data structure. You remove all the detail of room connections and replace this with a simple model. This is the third stage of computational thinking.
Algorithm
The final stage in computational thinking is called Algorithm design. This involves designing a series of ordered steps to solve a problem or achieve some end result, and refining these steps suitable for automation by a computer.
A structured English version of the final solution:
set up MAP dictionary
set up DESCRIPTION dictionary
set up FINISH list of items
ask player name and greet
set start room to ‘foyer’
WHILE true
print description of current room using DESC
IF room is in FINISH dictionary THEN
break
END IF
ask player for new direction
IF direction is ‘quit’ THEN
break
END IF
create key by joining direction and room
IF key is in MAP dictionary THEN
Legal move and room = MAP[key]
ELSE
print cannot go in this direction
END IF
END WHILE
message game over
For you to do:
In your workbook:
- create your own MAP and DESC dictionaries.
- create your own FINISH list
- modify your end-of-game message
Done? Show your teacher and get a sticker! Do the challenge.