On 8/16/2011 7:33 AM, Paul Wray wrote:
Hello all
Ive had what I think is a great idea for pure-python templates (I can
almost hear the groans, bear with me...)
For the impatient, proof of concept is at http://pastie.org/2379978
demonstrating simple substitution, balanced tags using context manager,
subtemplates, and template inheritance.
I'm posting here to get opinions on:
* the merits of the idea, (or otherwise!)
* whether there are any established/mature templating systems that use
this approach, or whether its come up before,
* ideas for improvements and advice on other aspects such as sandboxing
* of course, to share the idea in case others want to use it
Background: Ive been working on an application that recursively renders
html/xml documents from heterogenoeus trees, with separate classes for
each document component. First I built my own renderer but was
dissatisfied with the repetitive code. Then looked at Mako and Jinja,
and used Jinja but was still disatisfied, because I still needed a
render method in each class to do preparation, and also the template
which was centrally managed by the Jinja loader and environment. I found
a way to call templates recursively via Jinja filters, but was not sure
that it wouldnt blow up in my face, so I also had separate calls to
render the children of each node, and then feed the value to the parent
template. I kept thinking that there must be a way to get the brevity
and clarity of declarative templates, plus the simplicity of pure python
loops, tests and function calls.
The idea:
Python syntax allows a statement to be a bare literal or identifier.
These have no effect on the program.
More generally, Python has expression statements, with the result of the
expression ignored. These are usually function calls with side-effects.
"print('x')" has no effect on the program and the return value is
usually ignored.
So the function below is legal python:
def myFunc():
'a'
x = 45
'b'; 'c'; x
So is this (within the appropriate class context of course):
def body(self, r):
'<h1>'; self.heading; '</h1>'
'<ul>'
for itm in self.items:
'<li>'; itm; '</li>'
'</ul>'
The idea is simply to use python ASTs to transform this code so that it
accumulates the values of the bare expressions.
Interesting idea, though I have no experience for comparison.
--
Terry Jan Reedy
--
http://mail.python.org/mailman/listinfo/python-list
