How to Sum Dictionary Elements by Same Key Value in Python

Learn how to sum the area values of dictionaries with the same key in Python using defaultdict, and explore improved structure with dataclasses.
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How to Sum Dictionary Elements by Same Key Value in Python

In the world of programming, especially when working with Python, we often encounter the need to manipulate and aggregate data structures. One common scenario is when you have a list of dictionaries and you want to sum values associated with the same key. This can be a bit tricky if you're unfamiliar with Python's data structures. In this guide, we will walk you through how to do this efficiently using defaultdict and how to refine your code by using dataclasses.

The Problem

Imagine you have a list of dictionaries, where each dictionary contains an id_sistema_productivo (a unique identifier for a production system) and an area (an associated value). Your goal is to sum the area values grouped by the same id_sistema_productivo. Here's a look at our initial list of dictionaries:

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Based on this input, the expected output would aggregate the areas, resulting in:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

Step 1: Understanding defaultdict

To achieve this, we can utilize defaultdict from the collections module, which helps handle missing keys by initializing them with a default value (in our case, an integer starting from zero).

Here's how you can implement this:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Creating the Result List

Once we have tallied the areas in the result variable, we can construct our output list using a list comprehension:

[[See Video to Reveal this Text or Code Snippet]]

Complete Code Example

Combining all the above steps, here’s how the complete code looks:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Improving Structure with dataclasses

For added clarity and structure, you can use Python’s dataclass, introduced in Python 3.7. This allows a more organized definition of your data structure:

[[See Video to Reveal this Text or Code Snippet]]

Using dataclasses in your implementation makes your intentions clearer and leverages built-in methods for better code management. The new list of dictionaries can be transformed into a list of Element instances:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Summing elements in a list of dictionaries by their keys can be efficiently achieved using Python's defaultdict. By implementing a more structured approach with dataclasses, we enhance the readability and maintainability of our code. With these techniques, you can create clean, efficient, and understandable Python programs that manipulate complex data structures.

Whether you're a beginner or an experienced developer, mastering these concepts will significantly improve your data management skills in Python.

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