Flask with multiple forms on a page posted using AJAX and returning a rendered form result

22 February 2020 Updated 22 February 2020 by Peter

While working on comments system for the first time I bounced into the problem of having multiple WTForms forms on a single page. On every page there also is the search form but this is not a POST form. It is doing a GET. The comments system uses two forms: Comment form Comment reply form The comment form is immediately below the content item, blog post or page, the comment reply form is initially ...
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A textarea with a character counter widget for Flask, WTForms and Bootstrap

15 February 2020 Updated 18 February 2020 by Peter

I hoped to tell you today that you could comment on the blog posts of this website now. That would have meant that I completed the first implementation of the comments system. Unfortunately I stumbled upon some problems, yes of course, I am a programmer, and one of them involved the TextAreaField. I just wanted a simple extended version of the WTForm TextAreaField, just add a character counter field ...
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Threaded comments using Common Table Expressions (CTE) for a MySQL Flask blog or CMS

8 February 2020 Updated 16 February 2020 by Peter

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Now that I have blog posts, pages and a contact form, I decided to implement the comments for the blog posts and pages. Not just flat comments but threaded comments, also called nested comments. Some months ago I read about this and I really liked Miguel Grinberg's article: Implementing User Comments with SQLAlchemy. As often Miguel starts with defining the problem and some hard core theory and explaining ...
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The mysterious Flask Application Context, my questions and answers

30 January 2020 Updated 30 January 2020 by Peter

When you start with Flask you read a bit about the Application Context, TL;DR. Do not know about you but I certainly did not understand it fully. What is app, what is current_app, what is the difference, you just start programming your application. All the time in the background there is this weird buzz: what exactly is the Application Context ... Then at a certain moment when using a class you instantiated ...
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WTForms image picker widget for Flask with Bootstrap 4 without extra Javascript and CSS

24 January 2020 Updated 24 January 2020 by Peter

When you sign up for this website you are assigned an avatar image. Of course you can change the avatar in 'your account' and this is done using an image picker. Many image pickers examples can be found on the internet. But this is a Flask site including WTForms and I want the image picker to be generated by the wonderful Jinja macro I am using, see also link below, ok, I modified it a bit. With this ...
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OWASP Zed Attack Proxy (ZAP) security testing

13 January 2020 Updated 13 January 2020 by Peter

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Time for joy or crisis: running the OWASP Zed Attack Proxy (ZAP) application to check vulnerabilities of our web application. Developers often know there are weak points in their code, but there always is a date of delivery. So why not use a tool that list the well-known and important ones? This is my first time using ZAP so if are an expert you best stop reading here. In the links below there ...
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Flask, Babel and Javascript language files

6 January 2020 Updated 9 January 2020 by Peter

This Flask website is multilanguage. The implementation is described in previous posts. So far all my translations were in the Python code and the HTML templates. On a few places I needed some translations in Javascript and did this by pulling this Javascript code inline in the HTML template. For example, for forms I needed: e.target.setCustomValidity('Please fill out this field.'); I ...
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Flask site penetration tests: security headers and the session cookie

27 December 2019 Updated 27 December 2019 by Peter

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 ...
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Docker on Debian / Ubuntu not respecting ufw firewall settings exposing ports

9 December 2019 by Peter

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, ...
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Docker containers suddenly using 192.168.0.0/16 instead of 172.17.0.0/16: services lost

27 November 2019 Updated 27 November 2019 by Peter

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, ...
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Welcome

This website is not finished. I started it because I wanted to learn Python, ORM and the framework Flask. And as I wanted to deploy it to my ISPConfig3 (Nginx + Mariadb) webserver I also had to dive into Docker. Read more