Creating a Dictionary in Python: Storing Key-Value Pairs

The basic syntax for creating a dictionary is as follows:


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dictionary_name = {
    key1: value1,
    key2: value2,
    key3: value3
}

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:

book = {

"title": "Pride and Prejudice",

"author": "Jane Austen",

"year": 1813,

"genre": "Romance"

}

print(book)


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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:

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

print(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.

book = {"title": "1984", "author": "George Orwell", "title": "Animal Farm"}

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


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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

Swipe to start coding

Create a dictionary named library that stores information about at least three books. Each entry in the dictionary should represent a book with the following format:

Key: The title of the book (as a string)
Value: The author of the book (as a string)

You can use the following data: