Course Content

Python Data Structures

Creating a Dictionary

The basic syntax for creating a dictionary is as follows:

Keys: must be immutable (e.g., strings, numbers, tuples). A list or another dictionary cannot be the key;
Values: can be any data type (e.g., strings, numbers, lists, other dictionaries).

Imagine you are managing a library and want to store information about a book. Here's how you can create a dictionary to represent the book's details:


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book = {
    "title": "Pride and Prejudice",
    "author": "Jane Austen",
    "year": 1813,
    "genre": "Romance"
}
print(book)

This dictionary uses strings as keys to store information about the book.

Dictionaries allow keys to be any immutable data type. For instance, you can use numbers as keys to create an index of library shelves:


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shelves = {1: "Classics", 2: "Science Fiction", 3: "Mystery", 4: "Non-fiction"}
print(shelves)

In this example, numbers are keys to map genres to specific library shelves.

Note

An immutable data type is a type of data that cannot be changed after creation. Examples include strings, numbers, and tuples.

What happens if keys are duplicated in a dictionary?

In Python, dictionary keys must be unique. If duplicate keys are provided when creating or updating a dictionary, the last occurrence of the key will overwrite the previous one. This means the dictionary will only retain the most recent value associated with that key.


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book = {"title": "1984", "author": "George Orwell", "title": "Animal Farm"}
print(book)  # Output: {'title': 'Animal Farm', 'author': 'George Orwell'}

In this case, the second "title" key with the value "Animal Farm" overwrites the first "title" key.

Task

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Create a dictionary named library to represent a small library. The dictionary should have three keys: title, author, and year. Each key should map to a specific value of your choice.

Decide the values for each key:

title: the name of the book.
author: the name of the writer.
year: the year the book was published.

Use curly braces {} to create the dictionary. Each key-value pair is written as key: value, separated by commas.

Here is a quick idea: "1984", "George Orwell", 1949.

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Section 2. Chapter 1

Creating a Dictionary

The basic syntax for creating a dictionary is as follows:

Keys: must be immutable (e.g., strings, numbers, tuples). A list or another dictionary cannot be the key;
Values: can be any data type (e.g., strings, numbers, lists, other dictionaries).

Imagine you are managing a library and want to store information about a book. Here's how you can create a dictionary to represent the book's details:


              1234567
            
book = {
    "title": "Pride and Prejudice",
    "author": "Jane Austen",
    "year": 1813,
    "genre": "Romance"
}
print(book)

This dictionary uses strings as keys to store information about the book.

Dictionaries allow keys to be any immutable data type. For instance, you can use numbers as keys to create an index of library shelves:


              12
            
shelves = {1: "Classics", 2: "Science Fiction", 3: "Mystery", 4: "Non-fiction"}
print(shelves)

In this example, numbers are keys to map genres to specific library shelves.

Note

An immutable data type is a type of data that cannot be changed after creation. Examples include strings, numbers, and tuples.

What happens if keys are duplicated in a dictionary?


              12
            
book = {"title": "1984", "author": "George Orwell", "title": "Animal Farm"}
print(book)  # Output: {'title': 'Animal Farm', 'author': 'George Orwell'}

In this case, the second "title" key with the value "Animal Farm" overwrites the first "title" key.

Task

Swipe to show code editor

Create a dictionary named library to represent a small library. The dictionary should have three keys: title, author, and year. Each key should map to a specific value of your choice.

Decide the values for each key:

title: the name of the book.
author: the name of the writer.
year: the year the book was published.

Use curly braces {} to create the dictionary. Each key-value pair is written as key: value, separated by commas.

Here is a quick idea: "1984", "George Orwell", 1949.

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 1

Switch to desktop for real-world practiceContinue from where you are using one of the options below