[Zope] how to check attribute or property of a object ??

hello, Every dtml-image object has width and height as a default property. I want to check if a dtml image object has width (attribute or property) > 1 something like <dtml-if expr="objectname.len('width')>1"> do something <dtml-else> do something else </dtml-if> can anybody please tell me the exact syntax ?? can i use len ?? thanks for the help.