Modifying Dictionary Values

You can change the value of a specific key in a dictionary by:

• Assigning a new value using square brackets
• Using the update() method

Example 1: Change Item Using Square Brackets

car = {
 "brand": "Ford",
 "model": "Mustang",
 "year": 1964
}
car["year"] = 2020
print(car)

Output:

{'brand': 'Ford', 'model': 'Mustang', 'year': 2020}

Explanation: We updated the value of the key "year" from 1964 to 2020.

Example 2: Change Item Using update() Method

car = {
 "brand": "Ford",
 "model": "Mustang",
 "year": 1964
}
car.update({"model": "F-150"})
print(car)

Output:

{'brand': 'Ford', 'model': 'F-150', 'year': 2020}

Explanation: The update() method changes the value of an existing key ("model") to "F-150".

Example 3: Add New Item with update() (if not already present)

car = {
 "brand": "Ford",
 "model": "Mustang",
 "year": 1964
}
car.update({"color": "Blue"})
print(car)

Output:

{'brand': 'Ford', 'model': 'F-150', 'year': 2020, 'color': 'Blue'}

Explanation: If the key doesn’t exist, update() will add a new key-value pair to the dictionary.

Square Brackets vs update()

Example 4: Update Multiple Keys at Once

student = {
 "name": "Alice",
 "age": 22,
 "course": "Math"
}
student.update({"age": 23, "course": "Python"})
print(student)

Output:

{'name': 'Alice', 'age': 23, 'course': 'Python'}

Explanation: Multiple keys ("age" and "course") are updated at once using a single update() call.

Example 5: Conditional Update

student = {
 "name": "Alice",
 "age": 22,
 "course": "Math"
}
if "year" in car:
   car["year"] = 2024
print(car)

Output:

{'brand': 'Ford', 'model': 'F-150', 'year': 2024, 'color': 'Blue'}

Explanation: This updates the value only if the key exists.

Conclusion

You can update dictionary values using either square brackets or the update() method. update() is more flexible when modifying multiple items at once.