I was over-simplifying - or, to put is less diplomatically, I screwed up - when I answered that the addition returned a string. As Chris pointed out, it made the explanation very confusing. My apologies
The objects handled by + and <= can be : - strings, integers, floats - instances of $TagClass instances (more precisely, of classes copied from $TagClass, one for each HTML tag) : they are wrappers around a DOM element. The DOM element itself is the attribute "elt" of the $TagClass instance - the document, represented by the keyword doc. Its attribute "elt" is the document (top of the DOM tree) - instances of $AbstractClass, a container with a list of DOM elements. This list is the attribute "children" of the $TagClass instance Depending of the objects types, a+b returns the following objects : string + string : string (!) string + $TagClass : $AbstractTag with children [textNode(a),b.elt] string + $AbstractTag : $AbstractTag with [textNode(b)]+ b.children The 2 latter are implemented by the method __radd__ of $TagClass and $AbstractTag, invoqued by the method __add__ of the string class $TagClass + string : $AbstractTag with [a.elt,textNode(b)] $TagClass + $TagClass : $AbstractTag with [a.elt,b.elt] $TagClass + $AbstractTag : $AbstractTag with [a.elt]+b.children $AbstractTag + string : $AbstractTag with a.children+[textNode(b)] $AbstractTag + $TagClass : $AbstractTag with a.children + [b.elt] $AbstractTag + $AbstractTag : $AbstractTag with a.children + b.children (any type) + doc : unsupported doc + (any type) : unsupported The operation x <= y does the following : string <= (any object) : comparison, if possible ($TagClass | doc) <= string | integer | float : adds textNode(str(y)) to x.elt ($TagClass | doc) <= $TagClass : adds child y.elt to parent x.elt ($TagClass | doc) <= $AbstractTag : adds DOM elements in y.children to x.elt $AbstractClass <= (any type) : unsupported - Pierre -- http://mail.python.org/mailman/listinfo/python-list
