Dictionaries #

In this lab, we will learn about dictionaries, another useful data structure.

[0] Setup #

💻 Start by cloning your lab-dictionaries repository in your cs9 folder.

cd desktop/cs9/unit_01
git clone https://github.com/the-isf-academy/lab-dictionaries-YOUR-GITHUB-USERNAME.git

[1] High 🗝 Useful Data Structure #

You already know about lists, which are a great way to store things that naturally come one after another, like subway stops on a subway line, or homework assignments in a class.

The structure of a list works well for things that have a natural order (like zodiac cycles), but what about things that don’t have a natural order to them?

A dictionary is another kind of data structure that is useful for information that does not have a natural order.

Dictionaries connect keys to values. For each unique key (for example, an animal name like 'pig'), a dictionary stores a unique value (like a translation 猪).

animal_dict = {
"rat": "鼠",
"ox": "牛",
"tiger": "虎",
"rabbit": "兔",
"dragon": "龙",
"snake": "蛇",
"horse": "马",
"sheep": "羊",
"monkey": "猴",
"rooster": "鸡",
"dog": "狗",
}

Values in a dictionary are accessed via the key. For example:

animal_dict['dog']

Will return:

'狗'

Keys can easily be added to a dictionary like so:

animaion_dict["pig"] = "猪"

You can loop through a dict in almost the same way you can loop through a list:

for english, chinese in animal_dict.items():
  print("English zodiac: {} - Chinese zodiac: {}.".format(english, chinese))

Will output:

English zodiac: rat | Chinese zodiac: 鼠.
English zodiac: ox | Chinese zodiac: 牛.
English zodiac: tiger | Chinese zodiac: 虎.
English zodiac: rabbit | Chinese zodiac: 兔.
English zodiac: dragon | Chinese zodiac: 龙.
English zodiac: snake | Chinese zodiac: 蛇.
English zodiac: horse | Chinese zodiac: 马.
English zodiac: sheep | Chinese zodiac: 羊.
English zodiac: monkey | Chinese zodiac: 猴.
English zodiac: rooster | Chinese zodiac: 鸡.
English zodiac: dog | Chinese zodiac: 狗.
English zodiac: pig | Chinese zodiac: 猪.

[Zodiac Year] #

💻 Let's run the file zodiac_year_finder.py. It’s inside the /introduction directory. Currently, it only tell you your zodiac in English.

> python3 zodiac_year_finder.py
What is your birth year? 2010
I was born in the year of the tiger.

💻 Use the animals_dict to add the Chinese translation to the English Sentence “I was born in the year of the ________”.

Your zodiac_year_finder.py should now output something like:

I was born in the year of the tiger.
我属虎

[2] Game Library #

Let’s imagine our school had a library of video games. We could use a dictionary and lists to organize each game by genre.

game_library_dict = {
    "Sports": ["Fifa", "NBA 2K", "Wii Sports"],
    "Puzzle": ["Sodoku", "Tetris", "Bejeweled","Mahjong"],
    "Multiplayer": ["Amoung Us","Fall Guys","Minecraft","Fortnite","Rocket League"],
    "RPG" : ["The Witcher 3","Skyrim", "World of Warcraft", "Persona 5", "The Legends of Zelda"]
}

Notice:

• each key is a string type
• each value is a list of string types

It’s up to you, to write functions that will return information about the game_library dict.

You will code the following functions in the library_functions.py:

• total_num_games()
• get_genres()
• num_games_per_genre()
• get_games_for_genre()

💻 total_num_games()

• Paramter: a dictionary
• Return value: an integer value representing the number of games in the given dictionary

💻 get_genres()

• Paramter: a dictionary
• Return value: a list of the genres available in a given dictionary

💻 num_games_per_genre()

• Paramters: a genre, a dictionary
• Return value: an integer value representing the number of games available for the given genre in the given dictionary

💻 get_games_for_genre()

• Paramter: a genre, a dictionary
• Return value: a list of games available for the given genre in the given dictionary

A helpful function:

[Testing] #

💻 Write tests to ensure each of your functions works as intended. Use library_test.py to test your functions sufficiently.

✅ CHECKPOINT:

Answer the following prompts in your notebook before submitting this lab:

0. What is a dictionary and why is it useful?
1. How would you use a dictionary to organize students by grade level?
2. Look at the “0. Planet Gravity” Do Now. How could you use a dictionary to better organize the information?

[Deliverables] #

⚡✨

💻 For this lab, you should push updates to the following files to Github.

• lab-dictionaries respository
  • zodiac_year_finder.py
  • library_functions.py
  • library_test.py

Also be sure to hand in your notebook with checkpoint questions.

[3] Extensions: Interactive Games Library #

Now that you’ve written the library_functions, it’s up you to put them to good use.

💻 Create a new file called, interactive_library.py

• viewing the total number of games
• viewing the genres
• viewing the games by genre

💻 Write a new file called, interactive_library.py

Here is an example:

------------------------------------
--Welcome to the CS Game Library--
------------------------------------

We have 17 total games.

We have the following genres:
  - Sports
  - Puzzle
  - Multiplayer
  - RPG

Select a genre to view the games available: Sports

We have 3 Sports games:
  - Fifa
  - NBA 2K
  - Wii Sports

------------------------------------
--------Thanks for visiting!--------
------------------------------------

💻 Be sure to push your new file to Github.

[Contributing to the library] #

How would you adjust your program to allow users to add games to the library?

Consider:

• How would you implement a menu system?
• How do you add things to a dictionary?

💻 Remember to push your work to Github.