Richard Moon wrote:

Please stop me going mad.

I created two python method. The first , called 'know_nothing' takes no parameters but returns the string "I know nothing", the second, called 'timesit" takes two parameters, multiplies them and returns the result. When I come to use them from within a DTML document why do I have to say <dtml-var "timesit(1,2)"> but <dtml-var know_nothing>

I assume the top one is short for <dtml-var expr="timesit(1,2)"> whereas the second is short for <dtml-var name=know_nothing> (or even <dtml-var name="know_nothing"> since that seems to work as well)

(am I right ?)

and I think I understand that the name attribute is actually a function call with no parameters - right ?

but why does <dtml-var expr="know_nothing" not return anything to the calling object ?

Just when you think you are getting the hang of it :-)

I *think* that <dtml-var know_nothing> is actually equivalent to <dtml-var expr="know_nothing()"> however I can't test this at the moment so I may be completely wrong :-). /Matt

On Wed, 23 Feb 2000, Richard Moon wrote:

Please stop me going mad.

I created two python method. The first , called 'know_nothing' takes no parameters but returns the string "I know nothing", the second, called 'timesit" takes two parameters, multiplies them and returns the result. When I come to use them from within a DTML document why do I have to say <dtml-var "timesit(1,2)"> but <dtml-var know_nothing>

I assume the top one is short for <dtml-var expr="timesit(1,2)">

This is correct.

whereas the second is short for <dtml-var name=know_nothing> (or even <dtml-var name="know_nothing"> since that seems to work as well)

(am I right ?)

Yes you are, on both counts.

and I think I understand that the name attribute is actually a function call with no parameters - right ?

Yes. The ZPublisher adds the required parameters when it invokes the method.

but why does <dtml-var expr="know_nothing" not return anything to the calling object ?

Because expr="know_nothing" is not actually _calling_ the know_nothing() method, it is simply referencing it. In Python, doing this would return a function object: <function know_nothing at d9a20> This may be what was returned by your expression dtml-var above (you can tell by looking at view source; your browser will try and render that as a <function> tag, and ignore it, so you won't see it on the page.) You can use <dtml-var expr="know_nothing()">, and ZPublisher will fill in the required parameters for you. Or, if you like, you can specify them yourself. The prototype for DTMLMethod.__call__ is: def __call__(self, client=None, REQUEST={}, RESPONSE=None, **kw) where: - client is commonly _.None, or this() - REQUEST is commonly _ - and you can specify variable values with keyword arguments If you want to call timest with two named parameters, val1 and val2, try: <dtml-var expr="timest(_.None, _, val1=1, val2=2)"> There is a lot more to this than what I've discussed here. Unfortunately, I know of no good reference or tutorial on the subject.

Just when you think you are getting the hang of it :-)

It has a tendency to sneak up on you like that. Don't let it freak you out, though; it's all worth it.

Richard Moon

--Jeff --- Jeff K. Hoffman 704.849.0731 x108 Chief Technology Officer mailto:jeff@goingv.com Going Virtual, L.L.C. http://www.goingv.com/