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I have been doing a lot of infrastructure-as-code (IaC) work for my team, recently. We are heavy users of Amazon Web Services (AWS) and use Terraform as our main IaC tool.

Over the past few weeks, I have spun up and torn down my fair share of AWS Lambdas using Terraform, and the AWS bug(s) highlighted here were spotted during this time.

The main issue is that Amazon S3 notifications created through AWS Lambda triggers on the AWS Lambda screen are not properly cleaned up when Lambda functions are deleted.

Also highlighted herein is that the use of Lambda function…


An elegant syntax for building collections

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Comprehensions are an elegant syntax for creating collections such as lists, sets, and dictionaries in Python. In this video, I showcase the use of comprehensions in Python to build, filter, and transform lists, sets, dictionaries.

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Contents

  1. Reverse Polish Notation (RPN)
  2. Example RPN expressions
  3. Source code
  4. Code walk-through

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 are also the less popular prefix and postfix notations.

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

  • Infix: operators are “in” between the operands
  • Prefix: operators are before (pre) the operands
  • Postfix: operators are after (post) the operands

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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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?
  • Setting up a local Redis server using Docker
  • Exploring basic Redis concepts using a CLI client
  • Building and using your own Python Redis library
  • Using a real Python library for Redis
  • Summary

Prerequisites

  • Docker
  • Python 3.6+

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. …

Onel Harrison

Software Engineer — Data & Machine Learning

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