Скачать или смотреть How to Create an Index List of True Elements from a List in Python

Discover how to extract the indices of consecutive `True` values in a list using Python without relying on additional libraries.
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How to Create an Index List of True Elements from a List in Python

Identifying specific elements in a list is a common task in programming. Today, we'll explore how to extract the starting indices of segments where True values are consecutively repeated in a Python list. This can be particularly useful in scenarios where you're working with boolean flags or binary states.

The Problem Statement

Imagine you have a list of boolean values, such as the following:

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

Your goal is to create a new list that contains the starting index of each segment where the True values appear. From the main_list, the expected output should be:

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

Additionally, if your input was like this:

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

The expected result would simply be:

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

The Solution

To achieve this, we can write a simple Python function without using any external libraries like NumPy or GroupBy. Below is the code that helps us accomplish this task:

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

Explanation of the Code

Custom Difference Function:

The function my_diff(my_list) computes the differences between consecutive elements.

It starts by checking if the first element is True (represented as 1) and constructs the list accordingly.

The expression [y - x for x, y in zip(my_list[:-1], my_list[1:])] efficiently captures the differences of the rest of the elements.

Finding Indices:

We then use a list comprehension to enumerate through the results of my_diff().

The condition if x == 1 checks for the transition from False to True, which indicates the start of a new segment of True values.

Result:

The print statement displays the final list of starting indices.

Conclusion

This approach provides a clear and concise way to identify the indices of True segments in a list without relying on external tools or complex operations. It highlights a fundamental pattern of finding differences in boolean values, which is both efficient and scalable.

With this method, you can easily adapt and use it for more complex lists or larger datasets, ensuring you always get the starting indices of your True segments.



Feel free to implement the code above in your projects, and happy coding! If you have any further questions, don't hesitate to ask!