[Tim]
Don't recall what that was, but creating a new scope on each iteration sounds hard to explain in Python.
[Andrew Koenig]
I don't think it's particularly hard to explain. For example, one way to explain it is to say that
for i in <<stuff>>: body
is equivalent to
for <<hiddenvar>> in <<stuff>>: local i = <<hiddenvar>> body
This explanation doesn't need to rest on recursion.
Sorry, but as a Python programmer that explanation makes little sense to me. In effect, it pushes the mystery into what "local" is supposed to mean, but there's nothing _already_ in Python that acts the way you need "local" to act. Scope in Python is defined wrt "blocks", so you need to phrase this in terms of blocks, and there are very few kinds of blocks in Python's execution model: A block is a piece of Python program text that is executed as a unit. The following are blocks: a module, a function body, and a class definition. Each command typed interactively is a block. A script file (a file given as standard input to the interpreter or specified on the interpreter command line the first argument) is a code block. A script command (a command specified on the interpreter command line with the `-c' option) is a code block. The file read by the built-in function execfile() is a code block. The string argument passed to the built-in function eval() and to the exec statement is a code block. The expression read and evaluated by the built-in function input() is a code block. That's from section "Naming and binding" of the Python Reference Manual. I expect most Python programmers have "module, function, class ... plus some weird stuff I don't much care about" in mind. Python's execution model also has a one-to-one correspondence between active blocks and execution frames (see the rest of that section), which would need to be snapped to consider a finer-grained notion of block that didn't have its own execution frame. In short, it's only easy to define this in Python, without invoking nested functions, if you don't have Python's execution model in mind to begin with.