## Blog Posts

### Bitwise Operators In Python

Jun 18th, 2021

When working with cryptographic algorithm and hashes, it’s quite common to operate at the bit and byte level. For those situations, Python provides functionalities to convert int to byte and vice versa and bitwise operators to operate on bits. In today’s post we will look at the different bitwise operators available with examples.

### How Time Based Otp Work

Jun 11th, 2021

One-time passwords (OTP) are a great way to provide a second factor of authentication to an application. They are commonly distributed through channels like SMS, voice call, email, or physical token generator - common with banks. Although very useful, each of those distribution channels have limitations on both side; for the user and for the application developer. For example, for the user, SMS or voice call needs network connectivity which isn’t always available, and from the application developer, we need to rely on third party SMS gateway or voice call gateway which don’t support all countries, making 2FA unavailable for some. HMAC-based OTP (HMAC) and later on Time-based OTP (TOTP) were algorithms invented to address those problems providing a way for a prover to generate a valid OTP without the need of the verifier to send it to the prover. In today’s post we will see an example of TOTP implementation and look at how it is constructed.

### Chrome Shortcuts

Jun 4th, 2021

As software developers the second application we spend the most time on after our text editor is our web browser. I have been using Chrome browser for years and only recently realised how often I was clicking around with the mouse to change tabs, pin tabs, or simply searching for options. Since then, I learnt few shortcuts that I now use daily, some shortcuts built-in and others brought by extensions. In this post I’ll go through the shortcuts.

### Jekyll Category Page

May 28th, 2021

After five years of writing with over 250 posts, I realised that it would be nice to have a page with all post categories that I’ve discussed so far. In today’s post we’ll look at how we can leverage site.categories from Jekyll to construct a category page.

### The Different Usages Of Asterisks In Python

May 21st, 2021

In Python, we often see asterisks being used for other operation than the infix operations like multiplication. In today’s post we will look at the other scenario were we encounter the asterisk and understand the meaning of it in those different contexts.

### Testing Rxjs Observable With Marble Testing

May 14th, 2021

In Angular, we often use RxJS observables. Since observables are dependent on time, it makes them to hard to test. To make our life easier, RxJS provides a TestScheudler which offers a function run providing helper functions accepting Marbles, a special syntax used to define a timeline of events. In today’s post, we will learn about the Marble syntax and see how we can use it to test the behaviour of our observable composition.

### Component Reuse Angular

May 7th, 2021

Angular Router reuses components when it sees fit. The act of reusing a component saves time as the framework doesn’t need to destroy and create back a new object, instead it emits new values onto the observable params and data of the route. In today’s post we dig into the details of when does the reusability of components take place and understand how it impacts route.data.

### Understand Dom Rendering With Angular

Apr 30th, 2021

Change detection and DOM rendering are functionalities handled by Angular framework. When we build applications, most time, we don’t really need to pay attention in how things gets rendered as we trust Angular to do its job. But in some cases, it is necessary to understand how the rendering work, for example when using test tools like Cypress which gets instances of DOM nodes to perform action on them. We can get into situation where the re-rendering of arrays detach DOM nodes which were used by our Cypress specification. In today’s post, we will take a look at how the DOM get updated by Angular when re-rendering nodes on component input updates.

### Setup Vscode With Python Unittest

Apr 23rd, 2021

Few months ago we talked about Python Unittest. We looked at it from the perspective of running from terminal which is a great way to quickly verify that our application is healthy. When it comes to debugging specific issue, running from terminal can be more tricky. In this post, we will look at how we can enable Unittest test discovery from Visual Studio Code with the Python extension in order to provider a quick and easy way to debug source code and allowing us to breakpoint in unit tests.

### Create Angular Reusable Components

Apr 16th, 2021

In previous post we looked at ViewChild which gave access to the elements within the view, and ContentChild which gave access to the elements within the decorated directive. Combining those two allows us to create reusable components flexible enough to allow users to define their contents. For example, creating a table component where we abstract away the way a table is constructed and the style applied to it, but leave fuill flexibility for the user of the table to define the content of each cell. In this post, we will look at how we can create a reusable card component which defines the look of a card but leaves the full control to the user to define its content.

### Exploring Sql Joins In Postgres

Apr 9th, 2021

Even after using SQL for years, I still get caught from time to time with join cardinality where the result of simple queries surprise me as I omit to consider the relationships between tables assuming one-to-one relationships. In this post, we will look at the different type of joins that Postgres supports and see how the cardinality affects the result.

### Interacting With Smart Contract On Local Ethereum Blockchain

Apr 2nd, 2021

In previous posts, we looked into how compilers worked in general and dived into Python in particular looking at how CPython was producing Bytecode which in turn was interpreted by the Python VM. In the world of Ethereum blockchain, smart contracts are the programs that run on the Ethereum VM (EVM). In the same way, smart contracts are compiled into Bytecode which are submitted to the blockchain, and end up being executed on each nodes the decentralized Ethereum blockhain. In today’s post we will be building an example of a smart contract written in Solidity and deploy it in a local Ethereum blockchain.

### Pyproject Toml

Mar 26th, 2021

Few weeks ago we talked about setuptools and setup.py. We demonstrated the configuration of a simple setup.py file in order to package a project. Although setup.py used to be the default way of packaging applications, Python has progressed to offer a more generic approach described in PEP 517 and PEP 518 with the pyproject.toml file. In today’s post we will look at the usage of pyproject.toml in the context of package management.

### How To Use Patch In Python Unittest

Mar 19th, 2021

When writing unit tests, we sometime must mock functionalities in our system. In Python unittest.mock provides a patch functionality to patch modules and classes attributes. In this post, we will look at example of how to use patch to test our system in specific scenarios.

### Python C Extension

Mar 12th, 2021

Few weeks ago we looked into CPython, the default implementation of Python. We saw that CPython is implemented in C and provides a way to declare extensions implemented in C to be used from Python. In this post we will look into a simple example of a module implemented in C and see how we can use it from the Python interpretor.

Designed, built and maintained by Kimserey Lam.