Why do I not have to define the variable in a for loop using range(), but I do have to in a while loop in Python?

Question

I have the following code using a for loop:

    total = 0
    for num in range(101):
       total = total + num
       print(total)

Now the

Answer 1

I'd like to approach this question from a slightly different perspective.

If we look at the official Python grammar specification, we can see that (approximately speaking), a while statement takes a test, while a for statement takes an exprlist and testlist.

Conceptually, then, we can understand that a while statement needs one thing: an expression that it can repeatedly evaluate.

On the other hand, a for statement needs two: a collection of expressions to be evaluated, as well as a number of names to bind the results of those evaluations to.

With this in mind, it makes sense that a while statement would not automatically create a temporary variable, since it can accept literals too. Conversely, a for statement must bind to some names.

(Strictly speaking, it is valid, in terms of Python grammar, to put a literal where you would expect a name in a for statement, but contextually that wouldn't make sense, so the language prohibits it.)