Template Render Engine alternatives and similar packages

Template Render Engine

Why TRender?

It is just another template render engine so why should one choose TRender? TRender was originally created for SiriDB which needed a fast and simple template engine.

• Fast: TRender is able to render the SiriDB main page 1000x in 0.03 seconds.
• Simple: Well, you have to decide for yourself if this is a good thing. TRender is not extensivery rich in its capabilities but still can include and extend templates, it has conditional statements, for loops and can use blocks and macros. The template language has some resemblance with Quik (another template engine) but is somewhat different.

Installation

The easiest way is to use PyPI:

sudo pip3 install trender

Quick usage

from trender import TRender
template = '@greet world!'
compiled = TRender(template)
output = compiled.render({'greet': 'Hello'})
print(output) # => Hello world! 

Basics

TRender uses a template as input. This template can be a string or filename. Some options like include and extend are only available when using a filename and template path. When initializing an instance of TRender it will compile the given template. Usually this will happen only once for each template. The TRender instance can then be rendered with a dictionary (we call this a namespace and we actually create a 'Namespace' instance from the given dictionary). TRender is optimized to render a compiled template very fast.

When using a filename we also need to specify a path, like:

TRender('base.template', path='path_to_file')

Note that path should be the root path for your templates. Assume we have the following path structure:

/templates/
/templates/pages/
 base.template
/templates/components/
 component.template

Then it is best to initialize TRender like TRender('pages/base.template', '/templates') so the engine will be able to find components/component.template when used inside your template.

Both #extend and #include are only available when using a template file, not with a simple string.

Using variable

Variable in a template are prefixed with an @ and optionally can be closed with an ! exclamation mark. A variable can only include alphabetic characters, digits and underscores. (And a ., but this has a special meaning to select nested variable). If you want to use a @ as a symbol in the template, add ! as an escape character.

Examples:

# Just render a simple variable...
TRender('@name is sweet').render({
 'name': 'Iris'
}) 
# Output => "Iris is sweet"

# Escape @ to render an email address...
TRender('@name@!@domain').render({
 'name': 'iris', 
 'domain': 'home.nl'
})
# Output => "iris@home.nl"

# Use nested variable (you can use nesting as deep as you want)...
TRender('@person.name is @person.age years old').render({
 'person': {
 'name': 'Iris', 
 'age': 4
 }
})
# Output => "Iris is 4 years old"

# Close variable when needed...
TRender('@name!IsSweet').render({
 'name': 'Iris'
})
# Output => "IrisIsSweet"

Comments

Comments should start with ## or a # followed by a space.

Example:

# This is a comment line
##This is a comment line too

Conditionals

Conditionals are very simple in TRender. We evaluate a simple value or allow a function for more complex conditionals. We start with #if followed by an optional #elif finally an optional #else and close with #end. If a conditional is not available in the namespace it will evaluate as false.

Simple example:

TRender('''
#if @sweet:
 I'm sweet
#elif @nice:
 I'm nice
#else:
 Don't know..
#end
''').render({'nice': True})
# Output => "I'm nice"

Complex example (actually it's not really complex...)

TRender('''
#if @old_enough(@person.age):
 I'm old enough
#else:
 I'm NOT old enough
#end
''').render({
 'old_enough': lambda age: age >= 18,
 'person': {'age': 37}
})
# Output => "I'm old enough"

Loops

We use #for loops and the loop should always close with #end.

Since an example explains more than words:

TRender('''
#for @person in @people:
 @person.name is @person.age years old
#end
''').render({
 'people': [
 {'name': 'Iris', 'age': 4},
 {'name': 'Sasha', 'age': 32}
 ]
})
# Output =>
# Iris is 4 years old
# Sasha is 32 years old

Blocks

Sometimes you want to define a block and re-use this block several times. As a name convention I like to write blocks using CamelCase.

Example:

TRender('''
#block Item:
 <li>@item</li>
#end
<ul>
#for @item in @items:
 #Item
#end
</ul>
''').render({
 'items': ['laptop', 'mouse']
})
# Output =>
# <ul>
# <li>laptop</li>
# <li>mouse</li>
# </ul>

Macros

Macros are like blocks, except that they will be compiled only once using the namespace where the macro is defined. For example if we had used a macro in the block example above, we would get two empty <li></li> items since @item was not available when defining the macro. As a name convention I like to write macros using UPPERCASE_CHARACTERS.

Include

Including files is only possible when using a template file as source. Includes happen at compile time so they have no extra costs during rendering.

Example:

# base.template
<h1>Let's include a file</h1>
#include another.template
<span>Yes, it worked!</span>

# another.template
<span>Please, include me...</span>

# Now compile and render the templates
TRender('base.template', '.').render()
# Output =>
# <h1>Let's include a file</h1>
# <span>Please, include me...</span>
# <span>Yes, it worked!</span>

Extend

Extend can be used to extend a template. This is ofter useful when we want to use a base template but start rendering another specific template. It's only possible to use extend when using a template file as source.

Example:

# base.template
<html>
<head>
<title>I'm a base template</title>
</head>
<body>
#CONTENT
</body>
</html>

# some.template
#extend base.template:
#macro CONTENT:
<span>This is just some content...</span>
#end <!-- End of CONTENT -->
#end <!-- End of extend base.template -->

# Now compile and render the templates
TRender('some.template', '.').render()
# Output =>
# <html>
# <head>
# <title>I'm a base template</title>
# </head>
# <body>
# <span>This is just some content...</span>
# </body>
# </html>

How to use TRender with aiohttp (web server)

TRender can used together with the aiohttp web server by using simple decorators for loading and rendering templates.

Example:

from trender.aiohttp_template import setup_template_loader
from trender.aiohttp_template import template
# The 'template' decorator can be used to load a template.
# we assume in this example that you have the following template:
#
# /my_template_path/base.template
#
# and you want to render this using the namespace:
#
# {'name': 'Iris'}
@template('base.template')
async def myhandler(request):
 return {'name': 'Iris'}
# This will setup the template loader. Make sure you run this only once, 
# after template decorators are initialized.
setup_template_loader('/my_template_path')
# Thats it!