- Create a colors class and color mapper for your application
- Using PyInstaller and Cython to create a Python executable
- IMAPClient and flattening the BODYSTRUCTURE
- Blocking unsafe resources in HTML email using BeautifulSoup
- Python Multiprocessing graceful shutdown in the proper order
- FastAPI + SQLAlchemy: Asynchronous IO and Back Pressure
- Using UUIDs instead of Integer Autoincrement Primary Keys with SQLAlchemy and MariaDb
- Python Multiprocessing graceful shutdown in the proper order
- SLQAlchemy dynamic query building and filtering including soft deletes
- Flask RESTful API request parameter validation with Marshmallow schemas
- Threaded comments using Common Table Expressions (CTE) for a MySQL Flask blog or CMS
- SQLAlchemy server-side datetime calculations
27 November 2021 0
I was implementing some charts with Chart.js and needed to pass colors from my Flask application to the template. The graph is a line graph and the number of lines can vary. With the graph I also show a table with the (numeric) values used in the graph. The lines have different colors, I choose them from a list of colors. The table of line values has a column for each line. I want the header cell ...
6 October 2021 0
You have created a Python application and want to distribute it. You probably have it running in a Python Virtual Environment. But customers don't have this setup, some may not even have Python installed. There are several programs that can convert your Python application into a single executable file. Here I am using PyInstaller. You may also want to protect some of your code and/or speed up some ...
27 September 2021 0
Application developers want to use proven solutions to create an application. Many times this works but with the IMAPClient package there are a number of things missing. The whole idea of IMAP is to get only what you request. Suppose you have an email with many attachments but you want to view or download only one of them. To be able to do this you need the 'body_number' of this attachment and then ...
30 August 2021 0
I have created an IMAP E-Mail Reader using IMAPClient and Flask. The IMAP E-Mail Reader decodes the email into valid HTML. Then it needs to display this HTML through the browser. Works fine, so far so good. In this post I describe how I implemented an option in my IMAP E-Mail Reader to block unsafe resources in the HTML. To do this, I use BeautifulSoup and Python's Regular expression operations. Why ...
16 June 2021 0
For a new project I needed a deamon process that must execute many, more or less identical, operations on different resources. In this case the operation is IO bound and I solved it by using ThreadPoolExecutor. So far, so good. Next I wanted to store the results in files. Of course we use a queue to communicate between processes. The worker() process uses q.put() to add items to the queue and the ...
4 June 2021 0
APIs are becoming more and more important. Companies want to share their data with customers. Or want to enable third parties to create applications based on their APIs. Few months ago I created an API with Flask, SQLAlchemy, Marshmallow and APISpec, it was not really difficult, and works fine. Then I read more about FastAPI, an API framework that also supports Python async out of the box. It is based ...
26 May 2021 0
I wanted to create a network between a database Docker container and an application Docker container, both having their own Docker Compose files. And I also wanted to make sure doing it right before implementing this in the actual docker-compose files. Test first baby ... I also did this some time ago but had to look into this again because Docker Compose now has a name option in networks section. ...
24 May 2021 0
I just completed my first FastAPI app. This app allows users to have their own items, meaning that the user data models all have a user_id field. Nothing special but as FastAPI introduces some things new to me, like Dependency Injection, I was unsure if my app would work the way I wanted. My question was: if I load test the API with many concurrent users, does it still work? Warning. Only run a load ...
22 April 2021 0
When you create an API, you want to document it and today it is obvious to use OpenAPI for this. I am already using the Marshmallow package. The same people also developed the package APIspec, with a Flask plugin in an additional package apispec-webframeworks. To present the OpenAPI documentation I use the package flask-swagger-ui and the package flask-jwt-extended is used to protect the endpoints. Below ...
30 March 2021 0
When you build a RESTful API the first thing you do is define the status codes and error responses. RFC 7807 'Problem Details for HTTP APIs' specifies the minimum parameters you should return. If you did not looked into this, I suggest you do. Of course you often want to include more details about what went wrong. APIs are for developers and we do want to make it easy for them to understand why a call ...
8 March 2021 0
For a new Flask application using WTForms and SQLAlchemy, I had many relationships between tables and was looking for the easiest way to manage these tables. The most obvious choice is to use the QuerySelectField and QuerySelectMultipleField present in the wtforms-sqlalchemy package. Since I haven't used them before, I created a small application to play with. Below I show you the code (development ...
17 January 2021 0
17 December 2020 0
While writing a script to check if websites correctly redirected to 'https:/www.' I thought to add some SSL certificate checks as well. This means I had to verify SSL certificates downloaded from a host. Is the certificate really for this website? Show me the expiration date. Is the certificate chain correct? And can we trust the certificate(s)? Initially I got stuck where many people got stuck because ...
27 November 2020 2
I know, there are many articles about this subject. But I thought it was useful to write a post about this because I did not know all the details. I assume your website can be accessed from the internet using a 'without-www' URL and a 'with-www' URL. This article is not about selecting a website URL for marketing purposes. Even if you are using a 'with-www' URL for your website, you can still communicate ...
25 November 2020 1
This is a short post about Flask and the config variable SERVER_NAME. Like many developers I bumped into this at a certain moment, and I thought I share my story. Hopefully this will prevent headaches for some. My websites must be available by typing the following addresses in the browser: https://example.com = 'without-www', and, https://www.example.com = 'with-www' Whats more, for this ...
29 October 2020 0
This is a post about how I use Docker and Docker-composer to develop and run my Flask website with Celery and Redis. There are many articles on the internet about this and if you are searching for them do not forget to search on Github.com. I just grabbed the bits and pieces and created my own setup. Before going into this I want to mention two other things that came up when adding Celery to Flask. The ...
10 October 2020 0
Being able to run asynchronous tasks from your web application is in many cases a must have. One way to achieve this is to use Celery. There are many articles on the internet and some examples are given. I really liked Miguel Grinberg's posts about Celery. Very clear, thank you Miguel. But Miguel's post and most other articles are just an introduction. When you start with Celery you suddenly realize ...
30 September 2020 0
I developed one Flask website on Docker but after some time when my code became more stable I wanted to use the same setup for other websites. For one website I made a copy because it had to work yesterday. But what I really wanted was to share all the code, and some of templates. Of course every website has its own static directory, logging directory, templates, etc. The main reason for sharing is ...
22 September 2020 0
This is a short post about something I wanted to do a long time ago and for which I finally found some time. It was not really a case of TL;DR (Too Long; didn't read), but more something like TLT;DR (Too Little Time; didn't read). As you probably know, the Docker .dockerignore file is used to prevent certain files and directories ending up in your Docker image. The Docker .dockerignore file is used ...
20 August 2020 0
The problem: I have a website that sends emails. The emails (meta) are stored in a database before sending to the Postfix MTA. Every email the website sends has a unique message-id, something like firstname.lastname@example.org. I want to check if the emails are actually sent and add this information to the email (meta) database records. Postfix has statuses like: status=bounced ...