Teaching the "range" function in Python 3

[Gregory Ewing]

Irv Kalb wrote:
> In Python 2, I easily
> demonstrated the range function using a simple print statement:
> 
> print range(0, 10)
> 
> I discussed how range returns a list.  I gave many examples of different
> values being passed into range, and printing the resulting lists.
> 
> Next, I introduced the concept of a for loop and show how you use it to
> iterate over a list, for example:
> 
> for number in [12, 93, -45.5, 90]: # Some operation using each number (for
> example, adding up al the numbers)
> 
> When that was clear, I would go on to explain how you could incorporate range
> in a for loop:
> 
> for someVariable in range(0, 10):

Don't start with range(). Start with lists, and introduce the for
loop as a way to iterate over lists. Leave range() until much later.
You should be able to go a *long* way without it -- it's quite
rare to need to iterate over a range of ints in idiomatic Python
code.

When you do get to range(), just say it returns an object that
produces a series of ints when you iterate over it. By now they
should have seen enough examples of other iterable objects --
lists, tuples, etc. -- that this will make sense.

DON'T call it a "generator", btw -- that term is reserved for
a very special kind of iterator, and range() isn't one of them.

-- 
Greg