how to create dictionary in python

Jordan Payton

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07-09-2024

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Creating a dictionary in Python is a fundamental skill every programmer should learn. A dictionary in Python is like a real-life dictionary: it stores data in key-value pairs, making it easy to look up information quickly. In this guide, we will walk through the steps to create dictionaries, explore their features, and understand how to manipulate them.

What is a Dictionary?

In Python, a dictionary is an unordered collection of items. Each item is stored as a pair of a key and a value. You can think of keys as the word you look up in a dictionary, and the values are the definitions or explanations of those words.

Example:

• Key: "apple"
• Value: "A fruit that is red or green and is sweet to taste."

Creating a Dictionary

Creating a dictionary in Python is straightforward. You can do it in several ways:

1. Using Curly Braces {}

This is the most common method to create a dictionary.

# Creating a dictionary with curly braces
fruits = {
    "apple": "A sweet red or green fruit",
    "banana": "A long yellow fruit",
    "cherry": "A small red fruit"
}

2. Using the dict() Function

You can also create a dictionary using the built-in dict() function.

# Creating a dictionary using the dict() function
vegetables = dict(
    carrot="An orange root vegetable",
    broccoli="A green flowering vegetable",
    spinach="A leafy green vegetable"
)

3. Using List of Tuples

Another method to create a dictionary is by providing a list of tuples (key-value pairs).

# Creating a dictionary using a list of tuples
snacks = dict([
    ("chips", "Crispy snack made from potatoes"),
    ("cookies", "Sweet baked treats"),
    ("popcorn", "Puffed corn snack")
])

Accessing Dictionary Items

To retrieve values from a dictionary, you use the keys.

print(fruits["apple"])  # Output: A sweet red or green fruit

Checking for Existence of a Key

You can check if a key exists in a dictionary using the in keyword.

if "banana" in fruits:
    print("Banana is in the dictionary!")

Modifying a Dictionary

You can add new key-value pairs, update existing ones, or remove them.

Adding a New Key-Value Pair

fruits["grape"] = "A small, round fruit that grows in clusters."

Updating an Existing Value

fruits["banana"] = "A long yellow fruit that is high in potassium."

Removing a Key-Value Pair

del fruits["cherry"]

Dictionary Methods

Dictionaries come with a variety of built-in methods that make working with them easier:

• keys(): Returns a view object displaying a list of all the keys.
• values(): Returns a view object displaying a list of all the values.
• items(): Returns a view object displaying a list of key-value tuple pairs.

print(fruits.keys())   # Output: dict_keys(['apple', 'banana', 'grape'])
print(fruits.values()) # Output: dict_values(['A sweet red or green fruit', 'A long yellow fruit that is high in potassium.', 'A small, round fruit that grows in clusters.'])
print(fruits.items())  # Output: dict_items([('apple', 'A sweet red or green fruit'), ('banana', 'A long yellow fruit that is high in potassium.'), ('grape', 'A small, round fruit that grows in clusters.')])

Conclusion

Dictionaries in Python are versatile and powerful tools for organizing data. By understanding how to create, access, modify, and utilize them, you will be well-equipped to handle various programming tasks efficiently.

Explore More!

To deepen your understanding of Python dictionaries, you may find the following articles helpful:

• Python Lists: A Comprehensive Guide
• Understanding Python Data Structures

Now that you know how to create and manipulate dictionaries in Python, you can start using them in your projects! Happy coding!