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2023-09-14 - Chaining methods in Python
Method chaining is a programming style in which multiple method calls are made on the same object, in sequence. Each method call returns the object itself, so the next method can be called on it without having to assign the object to a variable in between.
This can make code more concise and readable, as it can be written as a single line of code instead of multiple lines. It can also make code more efficient, as the object does not have to be passed around between methods.
2023-09-04 - Using environment variables in a devcontainer
Hardcoded variables are never a good idea and one solution is the update the during deployment with Ansible for example. Another option is to set read those variables from the environment and maintaining them via systemd via a separate environment file or as part of the container deployment.
The example below is how Django reads the environment variables to configure the database connection to Postgresql. This way the application can easily be configured as is described in Environment variables set by systemd and the application itself never has to be modified or redeployed.
2023-09-01 - Reporting Flake8 finding as GitHub Annotations
In Extending GitHub Actions with Annotations the output of GitHub Actions was transformed into Annotations that could be shown in the web interface. The example shows that part for Flake8 which is a framework for different plugins to be combined and scan Python code on common mistakes and improvements. But later in 2023 a plugin was release for Flake8 to generate a report that can be used by GitHub Annotations.
By changing to GitHub Actions workflow file as shown in the example below, then the plugin flake8-github-annotations is installed and the flake8 commands are executed with the option
--format githublike as with yamllint. The lines to add the probem matcher can also be removed.2023-07-29 - Check Python with Flake8 Bugbear
Flake8 is a Python tool that checks Python code for style, programming errors, and help reduce code complexity. It is a wrapper around PyFlakes, pycodestyle, and Ned Batchelder’s McCabe script. Flake8 has a plugin structure and there are many plugins available. One of the plugins is Flake8 Bugbear. Flake8 Bugbear is a plugin for Flake8 that finds likely bugs and design problems in your program. It is a plugin for Flake8 that adds rules from the community that are not included in the core flake8 package.
As Flake8 Bugbear is a plugin for Flake8, you need to install Flake8 first. You can install Flake8 Bugbear with pip for example and in the example below Flake8 Bugbear is installed into a virtual environment.
2023-07-27 - Use systemd timers to make PostgreSQL backups
Systemd timers are a great way to replace cron jobs. They are more flexible and can have dependencies that can defined in easy statements instead of creating a script to check for the dependency. One of the use-cases is to use systemd timers to create PostgreSQL backups and remove old backups. In this example, we will create a backup of two databases, db1 and db2, and remove backups older than 10 days.
First step is to install PostgreSQL on the system. This example is for Debian or Ubuntu and uses the root user to connect to the database. It is recommended to create a user with limited privileges to connect to the database.