Records

5.3. Records#

A record is a data structure that allows you to store a fixed number of related pieces of information together as a single entity. Each piece of information in a record is called a field, and every field typically represents a specific attribute or property of the entity being described and fields do not have to have the same type (unlike arrays).

Think of a record like a form you might fill out at a doctor’s office. The form contains fields such as your name, age, phone number, and address. All these fields together describe one entity—you. Similarly, in programming, a record groups together related data into a structured format, making it easier to organise and work with.

5.3.1. Records in Python#

In Python, a simple and efficient way to represent records is by using tuples. We can create a tuple the same way we create a list but a tuple uses parentheses (). A tuple is an immutable sequence of elements (meaning that once the tuple is created it can’t be modified), and its fixed structure makes it a great choice for representing records with a defined set of fields. Each position in the tuple corresponds to a specific field.

For example, suppose you want to represent a student record with their name, age, and the subjects they are taking. You can use a tuple like this:

student = (
    "Alex",
    17,
    ["English", "Maths", "Software Engineering", "Drama", "Textiles"],
)

Here:

  • The first field 'Alex' represents the student’s name.

  • The second field 17 represents their age.

  • The third field ['English', 'Maths', 'Software Engineering', 'Drama', 'Textiles'] represents the subjects they are taking.

To get values out of a tuple in Python we can index them the same as we do lists:

student = (
    "Jordan",
    17,
    ["English", "Maths", "Software Engineering", "Drama", "Textiles"],
)

# Accesses name
print(student[0])

# Accesses age
print(student[1])

# Accesses subjects
print(student[2])

# Accesses first subject
print(student[2][0])
Question 1

How many elements can a record have?

  1. 1

  2. 2-10

  3. 10-100

  4. As many as you want

Solution

D

Records can have any number of elements, but all records of the same type must have the same number of elements.

Question 2

Which of the following are a key feature of records?

  1. Curly brackets, i.e. {}

  2. Immutability

  3. Containing at least one string

  4. All records must be unique

Solution

Solution is locked

Question 3

How do you get the 14 out of this record:

record = (13, 14, 15, 16)

  1. record[-1]

  2. record[0]

  3. record[1]

  4. record[2]

Solution

Solution is locked

Code challenge: Catalogue A Library

Paige, a librarian, contacts you and asks you to write some code capable of cataloguing every book in their library. Paige asks that you store each book as a record since the details should never change and store the records as a list which may be updated as books are added or removed from the library.

Here is an example of a book

harry_potter = (9780747532699, "Harry Potter and the Philosopher's Stone", 'Fiction - Children')

Your task is to write one function which adds a record to the list and another which removes a record from the list, as specified below. These functions should be written in library.py.

Add_book specification (written in library.py)

  • name: add_book

  • parameters: books (list), ISBN (int), title (str), genre (str)

  • return: list of records with the new book added (list)

Remove_book specification (written in library.py)

  • name: remove_book

  • parameters: books (list), ISBN (int), title (str), genre (str)

  • return: list of books with the book matching the provided details removed (list)

Example (running from main.py)

import library

books = [(9780007348695, 'The Cat In The Hat', 'Fiction - Children'),
        (9780747532699, "Harry Potter and the Philosopher's Stone", 'Fiction - Children')]

books = library.add_book(books, 9780520201798, 'Frankenstein', 'Fiction - Horror')
books = library.remove_book(books, 9780007348695, 'The Cat In The Hat', 'Fiction - Children')
print(books)

[(9780747532699, "Harry Potter and the Philosopher's Stone", 'Fiction - Children'), (9780520201798, 'Frankenstein', 'Fiction - Horror')]

Hint

You can delete an element from a list using .remove(item). Here is an example

animals = ['lion', 'caterpillar', 'elephant', 'bee']
animals.remove('elephant')
print(animals)

['lion', 'caterpillar', 'bee']