Syntax: Dict Iteration

In Python, we can iterate over dictionaries in multiple ways: either by keys, by values, or by both keys and values simultaneously.

Iterating Through Dictionary Keys

To iterate over keys in a dictionary, you can directly use a for loop on the dictionary.

user = {
  "name": "Alice",
  "email": "[email protected]",
  "age": 24
}
for key in user:
  print(key)

> "name"

> "email"

> "age"

Iterating Through Dictionary Values

To iterate over values in a dictionary, you can use the .values() method.

user = {
  "name": "Alice",
  "email": "[email protected]",
  "age": 24
}
for value in user.values():
  print(value)

> "Alice"

> "[email protected]"

> 24

Iterating Through Dictionary Keys and Values Simultaneously

To iterate over both keys and values in a dictionary, you can use the .items() method.

user = {
  "name": "Alice",
  "email": "[email protected]",
  "age": 24
}
for key, value in user.items():
  print(key, value)

> "name" "Alice"

> "email" "[email protected]"

> "age" 24

Practice: Adding a Dictionary's Values

1. Create a dictionary scores with keys as student names and values as their corresponding scores.

2. Use a for loop to iterate over scores and print each student name and their score.

3. Calculate the average score of the students and print it.

> Average score: 85.0

scores = {
  "Alice": 90,
  "Bob": 80,
  "Charlie": 85
}
total = 0
for score in scores.values():
  total += score
print("Average score:", total / len(scores))

Practice: Iterating Through a Dictionary of Dictionaries

Imagine you have a dictionary student_data where each key is a student ID and the value is another dictionary containing that student's information: name, email, and GPA.

1. Create the student_data dictionary with at least three students.

2. Iterate over student_data and print each student's ID and name.

3. Calculate the average GPA of the students and print it.

> Average GPA: 3.5

student_data = {
  101: {"name": "Alice", "email": "[email protected]", "GPA": 3.6},
  102: {"name": "Bob", "email": "[email protected]", "GPA": 3.4},
  103: {"name": "Charlie", "email": "[email protected]", "GPA": 3.5}
}
total_GPA = 0
for student_id, info in student_data.items():
  print(student_id, info["name"])
  total_GPA += info["GPA"]
print("Average GPA:", total_GPA / len(student_data))

Awesome job! Understanding dictionary iteration is key to manipulating and analyzing data in Python.