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Learn how to efficiently split a list of dictionaries in Python based on the prefix of an attribute value using `defaultdict`.
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How to Split an Array into Categories by Attribute Value in Python

When working with arrays or lists in Python, you may encounter situations where you need to organize or categorize elements based on certain attribute values. One common example involves arrays of dictionaries containing event types that need to be grouped by their prefixes. This guide will walk you through a simple yet effective solution to this problem.

The Problem: Grouping by Attribute Prefix

Consider the following array of dictionaries:

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

In this example, each dictionary has a type key with values that contain a prefix and a specific action (e.g., employee, job, meeting). Your task is to split this array into separate lists based on the prefix of the type attribute.

Is it necessary to go through the entire array for every prefix? Let's explore a more efficient method to achieve this.

The Solution: Using defaultdict

Instead of filtering through the array multiple times, we can use the defaultdict class from the collections module to dynamically create lists for each prefix as we iterate through the array just once. Below is the step-by-step approach:

Step 1: Import defaultdict

First, ensure you have the defaultdict available from the collections module:

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

Step 2: Initialize the defaultdict

Next, create an instance of defaultdict where each key will hold a list of items (events) corresponding to a particular prefix.

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

Step 3: Loop through the Array

Now, iterate over the original array and split the dictionaries based on the prefix in the type key:

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

Step 4: Resulting Dictionary Structure

After implementing the above loop, you will have a structured dictionary where each key represents a prefix and contains a list of all corresponding dictionaries. For example, if we run the initial setup with the following array:

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

The resulting dictionary will look like this:

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

Summary of Key Points

You can group arrays of dictionaries based on the prefix of an attribute using defaultdict for efficiency.

By iterating through your array just once, you save on computational resources compared to filtering multiple times.

This approach assumes that the type values will always contain a . (period), providing a clear means to split the string.

With this method, you'll effectively organize your data in a way that is both straightforward and performative. Happy coding!