5 4 2 Dictionary Methods Explained

Key Concepts

Dictionary methods in Python allow you to manipulate dictionaries, which are collections of key-value pairs. The key concepts include:

• Adding and Updating Elements
• Removing Elements
• Accessing Elements
• Dictionary Methods

1. Adding and Updating Elements

You can add new key-value pairs to a dictionary using assignment. If the key already exists, its value will be updated.

Example:

student = {"name": "Alice", "age": 25}
student["major"] = "Computer Science"
print(student)  # Output: {'name': 'Alice', 'age': 25, 'major': 'Computer Science'}

student["age"] = 26
print(student)  # Output: {'name': 'Alice', 'age': 26, 'major': 'Computer Science'}
    

2. Removing Elements

Elements can be removed from a dictionary using the pop() method, which removes the item with the specified key, or the clear() method, which removes all items.

Example:

student = {"name": "Alice", "age": 25, "major": "Computer Science"}
age = student.pop("age")
print(age)  # Output: 25
print(student)  # Output: {'name': 'Alice', 'major': 'Computer Science'}

student.clear()
print(student)  # Output: {}
    

3. Accessing Elements

You can access the value associated with a specific key using square brackets [] or the get() method. The get() method allows you to provide a default value if the key does not exist.

Example:

student = {"name": "Alice", "age": 25, "major": "Computer Science"}
name = student["name"]
print(name)  # Output: Alice

age = student.get("age", "Unknown")
print(age)  # Output: 25

gpa = student.get("gpa", "Unknown")
print(gpa)  # Output: Unknown
    

4. Dictionary Methods

Python provides several built-in methods to manipulate dictionaries. Some common methods include keys(), values(), items(), and update().

Example:

student = {"name": "Alice", "age": 25, "major": "Computer Science"}

keys = student.keys()
print(keys)  # Output: dict_keys(['name', 'age', 'major'])

values = student.values()
print(values)  # Output: dict_values(['Alice', 25, 'Computer Science'])

items = student.items()
print(items)  # Output: dict_items([('name', 'Alice'), ('age', 25), ('major', 'Computer Science')])

student.update({"gpa": 3.8})
print(student)  # Output: {'name': 'Alice', 'age': 25, 'major': 'Computer Science', 'gpa': 3.8}
    

Putting It All Together

By understanding and using dictionary methods effectively, you can efficiently manage and manipulate key-value pairs in Python.

Example:

student = {"name": "Alice", "age": 25}
student["major"] = "Computer Science"
student["age"] = 26

age = student.pop("age")
print(age)  # Output: 26

name = student["name"]
print(name)  # Output: Alice

gpa = student.get("gpa", "Unknown")
print(gpa)  # Output: Unknown

student.update({"gpa": 3.8})
print(student)  # Output: {'name': 'Alice', 'major': 'Computer Science', 'gpa': 3.8}