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Reverse Polish Notation (RPN)

Reverse Polish notation (also known as postfix notation) is one of multiple notations for representing mathematical expressions. Most of us are familiar with infix notation, but there is also the less popular prefix and postfix notations.

The most obvious difference among these lie in the position of operators in the expression.

Other differences include the significance of space as a separator (prefix and postfix are space sensitive while…


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Maybe you’ve been writing classes and creating objects in Python but never really thought about what the __init__ method was doing or what self meant. Or maybe this is all new to you.

Either way, I explain these two things in this video.

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Data structures organize data in ways that make it efficient for their data to be accessed in particular ways by placing constraints on how the data is accessed. Data structures may also place constraints on the data itself, such as a uniqueness constraint on items in a set — I talk about that in Set Basics in Python.

In this video, I talk broadly about data structures, briefly about stacks, and at length about queues and the deque Python module for easily creating and using queues.

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A domain-specific language for UML diagrams and more

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I’m taking a course in Knowledge-based Artificial Intelligence and Cognitive Systems. One of my assignments required that I create a state diagram that illustrates the complete state space an agent would search for a goal state for a relatively simple problem. I used PlantText, an online editor for PlantUML, to complete the assignment with more ease than using a GUI diagramming tool.

I talk more about this and show how you can get started with PlantUML in this video.

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In this video, I discuss Python’s native Set data structure, its frequently used methods, and situations in which using the Set data structure may be appropriate.

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More Computing resources

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I am learning image processing techniques to build an AI agent that can solve Raven’s Progressive Matrices test. Python is my language of choice, and Pillow — the friendly PIL (Python Imaging Library) fork — seems like a good place to start.

In this video, I inspect the metadata of the images I’ll later process while building my AI agent.

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Explore the concepts and build a library

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Contents

Prerequisites

What Is Redis?

The Redis docker page says that it is “an open-source, networked, in-memory, key-value data store with optional durability.” This description captures the key (nice unintentional pun) features of Redis.

Open source — Anyone can inspect Redis’ code or contribute to the project.

Networked— Redis uses the client-server model, in which communication between clients and servers happens over a network. In this…


I arrived in the United States (U.S.) several years ago to pursue an undergraduate education as an international student . There is a lot I could say about the international student experience in the U.S., but the purpose of the short post is to share some of the resources I have found helpful for keeping me informed about relevant immigration policies and filing procedures.

When I talk about my experience as an international student, I sometimes mention that in addition to the formal education I received, I also received an informal one in U.S. …


Microsoft’s releases of the Windows Subsystem for Linux (WSL) and Windows Terminal were causes for much excitement as they signified Microsoft’s commitment to improving the developer experience on Windows. There is still much to be desired from both products, but they have already significantly improved the developer experience on Windows.

Windows Terminal showing “Hello, world!” in Vim

One of the issues I have with Windows Terminal is the annoying sound that gets triggered when I hit a text or navigation boundary using the tab, backspace, or arrow keys. Apparently, that sound is a bell, and it is left on by default. …


Using the boto3 library and s3fs-supported pandas APIs

Image showing pandas data frame being read from and written files on Amazon S3
Image showing pandas data frame being read from and written files on Amazon S3

Contents

⚠ Please read before proceeding

There is an outstanding issue regarding dependency resolution when both boto3 and s3fs are specified as dependencies in a project. See this GitHub issue if you’re interested in the details.

This is still an issue as of 2021–02–19.

If you need both packages (e.g. to run the following examples in the same environment, or more generally to use s3fs for convenient pandas-to-S3 interactions…

Onel Harrison

Software Engineer — Data & Machine Learning

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