Dictionary Methods

Part of the Logic & Flow section of Coddy's Python journey — lesson 12 of 78.

Dictionaries, just like lists, come equipped with a variety of built-in methods to perform common operations. These methods can help you manipulate dictionaries more efficiently. Let's explore some of the key methods:

keys(): Returns a view object that displays a list of all the keys in the dictionary.

my_dict = {'name': 'Alice', 'age': 30, 'city': 'New York'}
keys = my_dict.keys()
print(keys)
# Output: dict_keys(['name', 'age', 'city'])

values(): Returns a view object that displays a list of all the values in the dictionary.

values = my_dict.values()
print(values)
# Output: dict_values(['Alice', 30, 'New York'])

items(): Returns a view object that displays a list of a dictionary's key-value tuple pairs.

items = my_dict.items()
print(items)
# Output: dict_items([('name', 'Alice'), ('age', 30), ('city', 'New York')])

get(key, default): Returns the value for the specified key. If the key is not found, it returns the default value (or None if no default is specified).

age = my_dict.get('age')
print(age)
# Output: 30

country = my_dict.get('country', 'USA')
print(country)
# Output: USA

pop(key): Removes the element with the specified key and returns its value.

city = my_dict.pop('city')
print(city)
# Output: 'New York'
print(my_dict)
# Output: {'name': 'Alice', 'age': 30}

Challenge

Easy

In this challenge, you'll work with a dictionary of student grades to practice essential dictionary operations.

Follow these steps in order and use the exact print statements shown:

Create a dictionary named grades with these initial key-value pairs:
- "Alice": 85
- "Bob": 90
- "Charlie": 78
Print all student names and grades using these exact statements:
- print("Students:", grades.keys())
- print("Grades:", grades.values())
Add a new student "Diana" with a grade of 92.
Use the get() method to retrieve Bob's grade, store it in a variable called bobs_grade, and print it using:
- print("Bob's grade:", bobs_grade)
Remove "Charlie" from the dictionary using the pop() method and then print the updated dictionary using:
- print("Updated grades:", grades)

Important: Follow the exact sequence and use the exact print statements shown above to match the expected output.

Expected Output:

Students: dict_keys(['Alice', 'Bob', 'Charlie'])
Grades: dict_values([85, 90, 78])
Bob's grade: 90
Updated grades: {'Alice': 85, 'Bob': 90, 'Diana': 92}

Cheat sheet

Dictionary methods for common operations:

keys(): Returns all dictionary keys

my_dict = {'name': 'Alice', 'age': 30, 'city': 'New York'}
keys = my_dict.keys()
print(keys)
# Output: dict_keys(['name', 'age', 'city'])

values(): Returns all dictionary values

values = my_dict.values()
print(values)
# Output: dict_values(['Alice', 30, 'New York'])

items(): Returns key-value pairs as tuples

items = my_dict.items()
print(items)
# Output: dict_items([('name', 'Alice'), ('age', 30), ('city', 'New York')])

get(key, default): Returns value for key, or default if key not found

age = my_dict.get('age')
print(age)
# Output: 30

country = my_dict.get('country', 'USA')
print(country)
# Output: USA

pop(key): Removes and returns value for specified key

city = my_dict.pop('city')
print(city)
# Output: 'New York'
print(my_dict)
# Output: {'name': 'Alice', 'age': 30}

Try it yourself

# Step 1: Create the Grades Dictionary
grades = {
    # Add initial student grades here
}

# Step 2: Access All Keys and Values
# Print all students and grades

# Step 3: Add a New Student
# Add Diana with a grade of 92

# Step 4: Retrieve a Student's Grade
# Get Bob's grade using get() method

# Step 5: Remove a Student
# Remove Charlie using pop() method
# Print the updated dictionary