mbelletti / yatl

Yatl - Web2py template language

Yet Another Template Language

This is the web2py template language described here made available as stand alone package so it can be used anywhere.

Basically it is pure Python within "{{" ... "}}" delimiters and blocks are terminated with "pass" if termination is not obvious. There is no indentation constraints.

For example:

from yatl import render, SPAN

example = """
<div> 
{{ for k in range(num): }}
<span>{{=SPAN(k, _class='number')}} is {{if k % 2 == 0:}}even{{else:}}odd{{pass}}</span>
{{ pass }}
</div>
"""

print(render(example, context=dict(num=10, SPAN=SPAN), delimiters="{{ }}"))

In the example SPAN is an optional helper. Output is escaped by default unless marked up with the XML helper as in {{=XML('1 < 2')}}. Note that the helpers included here are similar but not identical to the web2py ones. They are 99% compatible but the implementation is different.

Any Python expressions is allowed in templates, including function and class defintions:

example = """
{{ def link(x): }}<a href="{{=x}}">{{=x}}</a>{{ pass }}
<ul>
  {{ for k in range(num): }}
  <li>
     {{= link('http://example.com/%s' % k) }}
  </li>
  {{ pass }}
</ul>
"""

print(render(example, context=dict(num=10), delimiters="{{ }}"))

Caching

If you implement a caching reader as the one below, you mak yatl even faster:

CACHE = {}
def reader(filename):
    if filename in CACHE:
        return CACHE[filename]
    with open(filename) as fp;
        CACHE[filename] = content = fp.read()
    return content
      
output = yatl.render(reader(filename), path=path, reader=reader)