The technology

Introduction

AnPyLar is a Python framework for the web and it achieves this feat by piggybacking on *Brython* and distributing it packaged inside anpylar.js

Brython is an incredible project and an awesome achievement. And AnPyLar has contributed patches to the upstream to improve it, like for example improved metaclass support.

During the development of AnPyLar the auto-loadable packages for Brython were also invented.

But Brython is also a dynamic and changing environment and this has its drawbacks:

  • Pointing simply to the latest version of Brython could mean that AnPyLar applications would break.

That’s the reason for packaging a well-known (and possibly patched) version inside anpylar.js.

Some things to take into account

Being incredible and awesome doesn’t imply it is a complete and 100% CPython compatible implementation. It is by far complete enough to create very complex applications (AnPyLar being a good example of it) but this does come with some price tags, that you as developer have to take into account.

Let’s see them and avoid surprises later

  • It’s not a complete Python 3.x implementation and even the implemented areas may have some quirks. Don’t let this put down your idea to use this incredible technology, because it can do almost everything Python 3.x can do
  • It’s slower than Javascript. This should come to no surprise, because it’s written (and your scripts transpiled to) in Javascript. And yes, Python itself is slower than Javascript to start with due to its incredible dynamism and introspection possibilities.
  • Error reporting on the developer console can be difficult to process and understand. It just takes time. There are two things to do here
    • Modify little things and test. This will allow you to track only a small amount of changes to track to find the error
    • Use anpylar-syntaxcheck (abbreviate it to anpylar-syntax if you want) and give it a list of files/directories to check the syntax of your scripts before running them (or after having seen an error). It uses the built-in Python Abstract-Syntax-Tree facilities to find syntax errors in your code.

On the positive side

You are developing in Python in the browser and you can create incredible applications (complex or not)

Just do it!