Sebal writes:
<dtml-let x=fmod(sequence-index,4))>
Three standard problems: 1. attribute values for "let" that are not enclosed in "..." are treated as names and looked up: the code above tries to look up an object with name "fmod(sequence-index,4))" - quite hopeless You an expression rather than a name, enclose in "..." 2. "sequence-index" is a valid DTML name but it is invalid in Python. More precisely, it is interpreted there as "sequence - index", a subtraction not a name. You need "_['sequence-index']" 3. I never saw "fmod". Is it a Python built-in? Anyway, even if it were, it would not be available in DTML. (Some) Python built-in are available as attributes of "_". Other built-in functions are not available. After this didactic excursions, a short answer to your question: <dmtl-let x="_['sequence-index'] % 4 == 0"> "%" (applied to numbers) is Python's "mod" operator. Dieter