Steven D'Aprano <[EMAIL PROTECTED]> writes: > In *general* the compiler can't tell, but in specific cases it > could. A (hypothetical) optimizing compiler would tell the > difference between: > > for item in alist[1:5]: > print item # no possible side-effects
The 'print' statement converts the 'item' to a str. That conversion could, in a pathological case, have a side-effect (say, if the class of 'item' had an overridden '__str__' method with side effects), and the compiler can't know this isn't a pathological case. > for item in alist[1:5]: > alist.append(item) # side-effects DON'T matter The compiler doesn't know that, at the time of invocation, 'alist.append' doesn't have side effects that matter. The compiler for a dynamic language like Python has very little absolute "no significant side-effect in these specific cases" guarantee of the kind you're assuming even in the cases you choose for contrast with the ones that *do* have significant side-effects. -- \ "When we call others dogmatic, what we really object to is | `\ their holding dogmas that are different from our own." -- | _o__) Charles Issawi | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
