Building a toy template engine in Python

[alexmic]

http://alexmic.net/building-a-template-engine/

[js2]

A nice complement to this article is http://effbot.org/zone/simple-top-down-parsing.htm and its earlier piece http://effbot.org/zone/simple-iterator-parser.htm

Also, this page maintains links to many python parsing options - http://nedbatchelder.com/text/python-parsers.html

[thisishugo]

I'm not sure I like the idea of parsing templates with regular expressions. There is a better way, as demonstrated in Robe Pike's video[1] detailing how the Go template language is implemented.

Edit: which isn't meant to detract from the fact that this is a great article.

[1]http://www.youtube.com/watch?v=HxaD_trXwRE

[alexmic → thisishugo]

Thanks for the video – this was my first stub at template engines so I'm all for learning about better approaches.

[paradox95]

Try Pyxl

https://github.com/dropbox/pyxl

I don't work at Dropbox but I did work at Cove where this was originally developed and it is great. Makes working with HTML in Python so easy.

I also my own version of it that I have rewritten to treat the HTML object more like jQuery does and added more jQuery methods to it.

[peterldowns]

Great blog post! I did something very similar when I was working on an implementation of the Mustache templating language. If you haven't built a simple recursive descent parser already, I highly recommend doing so — it helped me get a lot better at programming.

[jamesconroyfinn]

I was particularly interested in building parsers a short while back, and your post rekindled my interest.

So, in the interest of sharing I thought I'd mention a couple of interesting libraries I came across.

In Ruby I think Temple (https://github.com/judofyr/temple) is really quite cool. It's designed to make creating templating languages really easy, and constructs ASTs using user-defined parsers.

And even more interesting in my opinion is Haskell's Parsec (http://www.haskell.org/haskellwiki/Parsec). It uses combinators to build up parsers, and can produce friendly parse error messages "for free."

Thanks for the intersting read.

[thomaslee]

Interesting extension of this exercise would be to replace your custom AST with the AST exposed by Python, then use the compile() builtin to compile said AST into a PyCodeObject ready for direct execution by the Python VM. :)

Something along these lines: https://github.com/thomaslee/viking-poc/blob/master/viking#L...

(Disclaimer: I wrote the Python-AST-to-PyObject transformation code for Python 2.6 that made this sort of stuff possible -- fun hack!)

[tomasandrle]

Interesting! I just finished writing a very similar engine in C++. https://github.com/catnapgames/NLTemplate

[marinos]

thanks for sharing this alexmic. I tried to built my own template engine but I think your approach is much better

[alexmic → marinos]

Thanks – what was your approach?

[fredsters_s]

really nice conceptual approach.

[CMGS]

jinja2 slower than django?