How to Update Python Dictionary Values with Other Values

What will you learn?

In this tutorial, you will learn how to update and modify the values of a Python dictionary based on specific criteria or conditions. This includes scenarios where you may need to increment or decrement values based on certain requirements.

Introduction to the Problem and Solution

Working with dictionaries in Python often involves updating values based on various conditions. One common scenario is when you have a dictionary containing data and need to adjust these values according to specific criteria. By iterating through the dictionary and applying conditional checks, you can efficiently update the values as needed.

For instance, if you have a dictionary storing student scores and want to award bonus points to students who scored below a certain threshold, you can easily achieve this by comparing scores and updating them accordingly.


# Dictionary of student scores
student_scores = {
    'Alice': 85,
    'Bob': 92,
    'Charlie': 78,
    'David': 88

# Add 5 bonus points to students scoring below 90
for student, score in student_scores.items():
    if score < 90:
        student_scores[student] += 5

# Print the updated scores

# Copyright PHD

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To update dictionary values based on other values, we iterate over each key-value pair in the dictionary using .items(). For each entry, we check if the score is below 90 and add 5 bonus points if it meets the condition. This allows us to efficiently modify specific values within the dictionary.

    How can I update multiple values at once in a Python dictionary?

    You can update multiple values simultaneously by iterating through the items in the dictionary and making necessary modifications.

    Can I use list comprehension to update dictionary values based on certain conditions?

    Yes, list comprehension provides an elegant solution for updating dictionary elements based on specified conditions effectively.

    Is it possible to change only specific keys’ values without iterating through all entries?

    Yes, you can directly access individual keys in a dictionary by their key names for updating specific entries without requiring extensive iteration.

    What happens if I try to access a key that doesn’t exist while updating a value?

    If you attempt to access a non-existent key while updating its value, Python will raise a KeyError indicating that the specified key is not present in the given dictionary context.

    How do I remove a key-value pair from a dictionary while updating its values?

    You can use the del keyword or pop() method to remove specific key-value pairs from a dictionary during value updates.


    In conclusion, manipulating Python dictionaries’ values based on predefined conditions involves strategically iterating over each item and implementing conditional logic for updates. Understanding how dictionaries operate enables efficient data manipulation tailored to specific requirements.

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