Learning about dictionaries

In Python, a dictionary is an unordered, mutable, and indexed data structure. It stores data in key-value pairs and provides a way to retrieve the value for any given key. Dictionaries are an important and versatile data structure in Python and are widely used in various kinds of programming tasks.

Creating a Dictionary

A dictionary in Python is defined by key-value pairs enclosed in curly braces {}, with pairs separated by commas. Each key-value pair is separated by a colon :. Here’s an example:

student = {
    "name": "Alice",
    "age": 20,
    "courses": ["math", "comp sci"]
}

Accessing Values

You can access the value for a given key using square brackets []:

print(student["name"])  # prints: Alice

If you try to access a key that does not exist in the dictionary, Python will raise a KeyError. To avoid this, you can use the get method, which returns None if the key is not found.

print(student.get("grade"))  # prints: None

Adding and Changing Items

You can add a new key-value pair to a dictionary by assigning a value to a new key:

student["grade"] = "A"

You can also change the value of an existing key the same way:

student["age"] = 21

Removing Items

The del keyword can be used to remove a key-value pair from a dictionary:

del student["age"]

Looping Through a Dictionary

You can loop through a dictionary to access its keys and values:

for key in student:
    print(key, student[key])

This will print each key and its corresponding value.

In summary, dictionaries in Python are a powerful tool for storing and managing data. They allow you to connect pieces of related information and efficiently access or modify them.