You created a Flask web application, it is running fine and using https. But is it secure enough? Did you do everything to protect your visitors, did you do everything to prevent malicious attacks? A good way to proceed on this is to pentest your site. Penetration testing tools, or pen testing tools, can identifying security weaknesses. They identify vulnerabilities in the web application that can ...

Again another unexpected Docker issue. In a previous post I described why and how you must force Docker to use a subnet, to prevent sudden unexpected changes in the network with consequences like mail no longer working. This post is about Docker not respecting firewall settings, at least when running Debian / Ubuntu and ufw (Uncomplicated Firewall). Docker does not tell you this, and exposes ports, ...

I have an ISPConfig server with Docker applications. They use the host Postfix mail transfer agent (MTA) to deliver mail to the outside world. Before using the send mail function I have a check if Postfix can be accessed. This works fine. But suddenly mail was not sent. The log file contained error messages like: 2019-11-26 17:31:56,758 ERROR MailMessage - send_mail: self.error_message = sending message, ...

For this website I am using Flask and SQLAlchemy without the Flask-SQLAlchemy extension. I need pagination for several pages. For example the home page holds the list of blogs and it should show a maximum of 12 items per page. It is not that difficult to implement. The home page view function requires a page_number that defaults to 1 if it not specified: @pages_blueprint.route('/', defaults={'page_number': ...

Probably many of you know only two mobile phone operating systems, iOS on Apple phones, and Googles Android on all other phones (some 80%). But there is also Ubuntu Touch (UT) originally developed by Canonical Ltd. and continued by UBports. I write a post about this because I am using UT on a Nexus 5 and wondered how difficult it would be to develop apps for it. When I discovered that you can use Python ...

While writing an application on my Docker platform I hit an unexpected problem, yes, another one ... This was the first time that I had to show the time on a page of a website running on Docker and it appeared that the time was UTC instead of local time. In the code I was just using the normal Python calls to get the time: import datetime ... now = datetime.datetime.now() hour = now.hour ...

How to implement Flask multilanguage is explained in the Flask docs, see links below. But this is just a starting point. You need deeper understanding of the process to handle special cases like falling back to a default language, language switching, and the 404 Page Not Found exception. Assumptions In the remainder of this post we are using a language code, 'lang_code', that is available in the ...

I run a server with ISPConfig with some 50 sites. The sites are static or PHP. I am developing Python Flask applications now and also want to run them on the ISPConfig server. You can create virtual environments on the ISPConfig server and run your application from here. But some time ago I have chosen to use Docker for development, staging and production. It takes time to set this up ...

The Flask application I am writing to run this website has all code in a single 'app'. I already did some reorganizing as I wanted full separation of frontend code and the administration code. Now it it is time for total separation, meaning making the frontend a Flask app and the admin another Flask app while both running in the same domain and both reside in the same project directory. Because we ...

Update 11 October 2019: I changed the addon-tag from '{% addon: ... %}' to '[[ addon: ... ]]'. The reason is that I wanted to be able to render the page text coming from the database, using render_template_string, and '{% ... %}' conflicts with Jinja2 tags. And yes, I do not want to implement a Jinja2 custom tag.  What is difficult about implementing a contact page with a contact form with Flask ...

Before you read on, you may want to read my previous posts about multilanguage and language fallback, see links below. When I gave myself the assignment to develop and implement a multilanguage Flask website with SQLAlchemy I knew things could get difficult. I did not really took the time to design everything beforehand, I just read a lot about multilanguage on the internet and trusted my experience ...

Before you read on, you may want to read my previous post about language fallback, see link below. Here you have an example of the complexity of multilanguage. The link should be shown in the language you are using at the moment ... another time.   Life is one long big sequence of problems we are solving all the time. It starts with getting enough oxygen, solved by breathing, maybe second ...

In a previous post I described the first version of the multilanguage database used on this website. For every table that has fields that must translated, we add a 'translation' table with these fields. I also implemented language fallback: if an item, like a blog post, does not exist in the selected language then the item of the (system-wide) default language is shown. This works fine but now I want ...

Update: Using reserved words is only working if you keep the words in place. I first substituted them for non-translatable tags but then DeepL does not know what it is doing anymore.  Of course nothing compares to a translation by a professional translator. Machine translation is difficult. DeepL tries to improve translations by machine learning but they are still far away from using the proper ...

Objects, it is nice to build an application with them but it has one very big disadvantage: it can be very slow because of the extra CPU-cycles and all the extra memory used. The slowdown of course is very much caused by the extra mapper layers and extra data.  Should you care about performance? Yes! The admin part of an application does not have to be very fast but the frontend pages, the pages ...

When I started this project, this website, I kept in mind that it had to support multiple languages. But of course I did not really look into database design because of all the other things I had to learn, add and implement. After a certain moment I could display and select multiple languages but that was for the texts in the code and templates and not for the database content items like blog posts ...

This post is about editing code, a lot of editing, huge amounts of editing! When you implement much functionality, you notice things that need attention, things that need you to research, how do others do this, what is the plural of certain words, etc. I maintain a todo list and every time I noticed something that needed attention I added it to this list. The list got too big so I decided to stop adding ...

With a single language there is not really a problem, we just forget about the rest of the world and build our single language Flask application. We start getting a headache when the website must support multiple languages. What exactly is a website supporting multiple languages? How many languages will be supported, and which languages? For English there are for example en-GB and en-US. Which parts ...

Performance is a never ending story. At a certain moment I noticed that putting the home page on the screen took some 370 milliseconds using the Flask development server with debug messages shown. That seemed far too long! How did I notice this? Because at the bottom of every page I show the time it takes to generate a page. Please note that the timings below are from a more optimized version of the ...

In Flask we have the config object which can be used to specify database parameters, email parameters, etc. When we run a Flask program it first creates the application. Once the application has been created subsequent requests skip the app creation and are redirected to the blueprint views. When Flask starts, the config variables are loaded and used. Important to understand is that every visitor ...