Wellcome to this insightful lesson where we’ll explore the powerful world of dictionaries in Python. Dictionaries are versatile data structures that allow us to store and retrieve data using key-value pairs. In this lesson, we’ll dive into the fundamentals of dictionaries, understand their structure, and explore various operations that can be performed on dictionaries.
Understanding Dictionaries:
1. Definition:
- A dictionary is a collection of unordered, mutable, and indexed elements.
- Elements are stored as key-value pairs, where each key must be unique.
- Syntax:
my_dict = {"key1": value1, "key2": value2, ...}
2. Accessing Values:
- Values can be accessed using their respective keys.
- Example:
my_dict = {"name": "Alice", "age": 25, "city": "Wonderland"}
print("Name:", my_dict["name"])
3. Modifying Values:
- Values associated with a key can be modified.
- Example:
my_dict = {"name": "Alice", "age": 25, "city": "Wonderland"}
my_dict["age"] = 26
Dictionary Operations:
4. Adding Key-Value Pairs:
- New key-value pairs can be added to a dictionary.
- Example:
my_dict = {"name": "Alice", "age": 25}
my_dict["city"] = "Wonderland"
5. Removing Key-Value Pairs:
- Key-value pairs can be removed using the
delkeyword or thepop()method. - Example:
my_dict = {"name": "Alice", "age": 25, "city": "Wonderland"}
del my_dict["age"]
6. Dictionary Methods:
- Dictionaries have various built-in methods, such as
keys(),values(), anditems(). - Example:
my_dict = {"name": "Alice", "age": 25, "city": "Wonderland"}
keys_list = my_dict.keys()
values_list = my_dict.values()
7. Dictionary Iteration:
- Iterating through keys, values, or key-value pairs.
- Example:
my_dict = {"name": "Alice", "age": 25, "city": "Wonderland"}
for key in my_dict:
print(f"Key: {key}, Value: {my_dict[key]}")
Example:
Let’s consider an example where we use a dictionary to store information about a person:
# Example Code
person_info = {"name": "Bob", "age": 30, "occupation": "Engineer"}
# Accessing values
print("Name:", person_info["name"])
print("Age:", person_info["age"])
# Modifying a value
person_info["age"] = 31
# Adding a new key-value pair
person_info["location"] = "Cityville"
# Removing a key-value pair
del person_info["occupation"]
# Iterating through keys and values
for key, value in person_info.items():
print(f"{key}: {value}")
Practice Exercise:
Create a Python script that uses a dictionary to represent a product in an online store. Include keys such as “product_name,” “price,” and “quantity_available.” Perform operations like modifying the price, adding a discount, and updating the quantity available.
# Example Practice Exercise
product_info = {"product_name": "Laptop", "price": 1200, "quantity_available": 50}
# Modifying the price
product_info["price"] = 1100
# Adding a discount
discount = 100
product_info["price_with_discount"] = product_info["price"] - discount
# Updating the quantity available
new_quantity = 40
product_info["quantity_available"] = new_quantity
# Displaying the updated information
for key, value in product_info.items():
print(f"{key}: {value}")
Summary:
In this lesson, we’ve explored the fundamentals of dictionaries in Python and learned how to perform various operations on them. Dictionaries provide a flexible and efficient way to manage data using key-value pairs. Practice using dictionaries to enhance your coding skills, and feel free to ask questions in the discussion forum. Let’s continue our Python journey with confidence in utilizing dictionaries!