8 ms·

Writing a Jinja-inspired template library in Python

27 points by makaimc 5y ago

danmur 5y ago
I seem to be in the minority but I'm not a fan of jinja2. I like mako better, I guess you have more leeway to do silly things but I never feel like I can't do what I want.
- deleted 5y ago
  [deleted]
- memco 5y ago
  Having never used Mako the appeal to me over Jinja is that it allows you to use real control structures. Jinja is a bit of a pain to debug and develop because it does some things slightly differently than you'd do in native Python so even though I can setup breakpoints and evaluate the application state I can't easily convert the code changes I make in the debugger back to the template. I get that there are reasons why Jinja and other templating systems guard against this, but it does have a cost.
  - jxramos 5y ago
    can you detail the idea about real control structures, are you talking about if and elif and else clauses? Is there something partial about jinja's control structures? https://jinja.palletsprojects.com/en/3.0.x/templates/#list-of-control-structures https://jinja.palletsprojects.com/en/3.0.x/templates/#list-o...
- simonw 5y ago
  I've seen a large scale Mako codebase and the amount of business logic that had sneaked into the templates was horrifying - really made me double-down on my preference for limited template languages that help people avoid that temptation. I helped design Django's template language and I now think we took keeping it restrictive a bit too far though - these days I prefer working with Jinja because it has better support for complex expressions and lets you call functions within your templates. That does mean it requires a bit more discipline to use responsibly though, but being able to control which functions are exposed to the template context helps a lot there.
- wodenokoto 5y ago
  I hate jinja. I really don’t get it. So here’s a complaining reply, so you hopefully won’t feel as alone. When using jinja2 for website builders, it just feels like a poor version of old school php. I’ve also seen it used for generating json/yaml config files, which to me is absolutely bunkers compared to just building a dictionary in Python and exporting it.
iamgopal 5y ago
Are there other template library in other languages ( especially in rust or go ) that converts templates in to native language code for execution? Like the way jinja do.
- giancarlostoro 5y ago
  In D, vibe.d does this. It uses a pug like syntax for templates. Edit: They've extracted the library into its own thing called diet-ng https://vibed.org/ https://vibed.org/ https://github.com/rejectedsoftware/diet-ng/ https://github.com/rejectedsoftware/diet-ng/
- denysvitali 5y ago
  Yes, there is pongo2 [0] and my runner (basically a small Go software that runs the template engine) pongo2-runner [1]. I'm not the author of the library (pongo2), but I'm using pongo2-runner to dynamically create config files out of environment variables, with custom logic. Super recommended. [0]: https://github.com/flosch/pongo2 https://github.com/flosch/pongo2 [1]: https://github.com/swisscom/pongo2-runner https://github.com/swisscom/pongo2-runner
  - eatonphil 5y ago
    Pongo2 is a tree walking interpreter from everything I see. It does not compile the templates into bytecode or native code before executing/interpreting.
    - denysvitali 5y ago
      Oh yes, sorry, misread that. Never mind then!
- conradfr 5y ago
  Twig, inspired by Jinja2. https://twig.symfony.com/ https://twig.symfony.com/
- shakna 5y ago
  Most template languages for Lua generate functions, that will be called with their own environment. Having first-class environments makes that the "obvious" way of doing things. For example, here's a 160LOC one I wrote a while back. [0] [0] https://git.sr.ht/~shakna/lserver/tree/master/item/template.lua https://git.sr.ht/~shakna/lserver/tree/master/item/template....
jxramos 5y ago
I was always hoping to find something that would do partial renderings of a template before some exception occurred while rendering said template. This would be a great debug feature. https://stackoverflow.com/questions/56084066/is-there-a-way-for-jinja-to-output-its-partially-rendered-content-before-an-exce https://stackoverflow.com/questions/56084066/is-there-a-way-...

27 points by makaimc 5y ago

I seem to be in the minority but I'm not a fan of jinja2. I like mako better, I guess you have more leeway to do silly things but I never feel like I can't do what I want.

deleted 5y ago
[deleted]
memco 5y ago
Having never used Mako the appeal to me over Jinja is that it allows you to use real control structures. Jinja is a bit of a pain to debug and develop because it does some things slightly differently than you'd do in native Python so even though I can setup breakpoints and evaluate the application state I can't easily convert the code changes I make in the debugger back to the template. I get that there are reasons why Jinja and other templating systems guard against this, but it does have a cost.
- jxramos 5y ago
  can you detail the idea about real control structures, are you talking about if and elif and else clauses? Is there something partial about jinja's control structures? https://jinja.palletsprojects.com/en/3.0.x/templates/#list-of-control-structures https://jinja.palletsprojects.com/en/3.0.x/templates/#list-o...
simonw 5y ago
I've seen a large scale Mako codebase and the amount of business logic that had sneaked into the templates was horrifying - really made me double-down on my preference for limited template languages that help people avoid that temptation. I helped design Django's template language and I now think we took keeping it restrictive a bit too far though - these days I prefer working with Jinja because it has better support for complex expressions and lets you call functions within your templates. That does mean it requires a bit more discipline to use responsibly though, but being able to control which functions are exposed to the template context helps a lot there.
wodenokoto 5y ago
I hate jinja. I really don’t get it. So here’s a complaining reply, so you hopefully won’t feel as alone. When using jinja2 for website builders, it just feels like a poor version of old school php. I’ve also seen it used for generating json/yaml config files, which to me is absolutely bunkers compared to just building a dictionary in Python and exporting it.

iamgopal 5y ago

Are there other template library in other languages ( especially in rust or go ) that converts templates in to native language code for execution? Like the way jinja do.

giancarlostoro 5y ago
In D, vibe.d does this. It uses a pug like syntax for templates. Edit: They've extracted the library into its own thing called diet-ng https://vibed.org/ https://vibed.org/ https://github.com/rejectedsoftware/diet-ng/ https://github.com/rejectedsoftware/diet-ng/
denysvitali 5y ago
Yes, there is pongo2 [0] and my runner (basically a small Go software that runs the template engine) pongo2-runner [1]. I'm not the author of the library (pongo2), but I'm using pongo2-runner to dynamically create config files out of environment variables, with custom logic. Super recommended. [0]: https://github.com/flosch/pongo2 https://github.com/flosch/pongo2 [1]: https://github.com/swisscom/pongo2-runner https://github.com/swisscom/pongo2-runner
- eatonphil 5y ago
  Pongo2 is a tree walking interpreter from everything I see. It does not compile the templates into bytecode or native code before executing/interpreting.
  - denysvitali 5y ago
    Oh yes, sorry, misread that. Never mind then!
conradfr 5y ago
Twig, inspired by Jinja2. https://twig.symfony.com/ https://twig.symfony.com/
shakna 5y ago
Most template languages for Lua generate functions, that will be called with their own environment. Having first-class environments makes that the "obvious" way of doing things. For example, here's a 160LOC one I wrote a while back. [0] [0] https://git.sr.ht/~shakna/lserver/tree/master/item/template.lua https://git.sr.ht/~shakna/lserver/tree/master/item/template....

jxramos 5y ago

I was always hoping to find something that would do partial renderings of a template before some exception occurred while rendering said template. This would be a great debug feature. https://stackoverflow.com/questions/56084066/is-there-a-way-for-jinja-to-output-its-partially-rendered-content-before-an-exce https://stackoverflow.com/questions/56084066/is-there-a-way-...