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

Python for loops assign the variable and let you use it. We can transform a for loop into a while loop to understand how Python actually does it (hint: it uses iterables!):

iterator = iter(iterable)  # fresh new iterator object
done = False
while not done:
    try:
        item = next(iterator)
    except StopIteration:
        done = True
    else:
        # inside code of a for loop, we can use `item` here
        pass