[Zope-CMF] taL: test evaluates all arguments

[Jeffrey P Shell]

On Friday, January 3, 2003, at 01:59  PM, robert rottermann wrote:

> if have the following tal statement:
>
> tal:define="resp_def  
> python:here.users_with_local_role('ObjectResponsible');
>          responsible python:test(resp_def == [], '', resp_def[0]);"
>
> When resp_def is an empty list I get an index out of range error.
> This seems very strange.
>
> can anybody give me a hint what goes wrong here ??

An alternate spelling that you can use is:

"responsible python:resp_def and resp_def[0] or ''"

While Python itself doesn't have the hideous 'a ? b : c' construct, you 
can simulate it with 'a and b or c' in an expression.  You can think of 
it as 'expr and iftrue or iffalse'

 >>> mylist = []
 >>> mylist and mylist[0] or "nope"
'nope'
 >>> mylist and mylist[0] or ''
''
 >>> mylist = ['Jeff']
 >>> mylist and mylist[0] or ''
'Jeff'



Jeffrey P Shell, jeffrey@cuemedia.com