[Edu-sig] What version of Python to teach ....

[Gregor Lingl]

Edward Cherlin schrieb:
> On Sun, Apr 19, 2009 at 12:07 PM, Laura Creighton <lac at openend.se> wrote:
>> One note:
>> It is very important to teach your students how to read code.  ...
...
>>
>> It would be interesting to go through this collection of examples
>> used in teaching 2.x, and find out how much of the new code just
>> works, and what are the remaining issues
It's certainly not the only issue, if code 'just works' or not. There 
are quite a few
differences between Python 2 and Python 3 that concern the semantics of 
code.

As a very elementary example consider the different meaning of

range(5)

in Python 2/3. Imho in this case at first it would be important to find
didactically clean ways  to explain  new concepts like these  to beginners.
Of course I know that these  concepts are not entirely new, but with
Python 3 they need to appear at a much  earlier  stage, e. g. when
introducing the for loop.

In 'former times' we could say: range(5) is a list (i. e. a container or 
a compound
data type) and the for loop does things for every element in this list. 
And you could view
this list:

>>> range(5)
[0, 1, 2, 3, 4]
>>> for item in range(5):
   print item

  
0
1
2
3
4
>>> type(range(5))
<type 'list'>

... easily to grasp

Now, with Python 3,  we have:

>>> range(5)
range(0, 5)
>>> for item in range(5):
       print(item)

  
0
1
2
3
4
>>> type(range(5))
<class 'range'>

How do you explain the nature of range to beginners? (Not a a rhetorical
question, I'd really like to know different approaches how to do it!)

At least you can see, that this is a much more important question
than e. g. the parentheses around item (because of print being a
function now  - but even here the semantic difference between a
function and a statement is the point and not the parentheses ...)

Regards,
Gregor