some problems for an introductory python test

[Hope Rouselle]

Mats Wichmann <mats at wichmann.us> writes:

> On 8/9/21 3:07 PM, Hope Rouselle wrote:
>> I'm looking for questions to put on a test for students who never had
>> any experience with programming, but have learned to use Python's
>> procedures, default arguments, if-else, strings, tuples, lists and
>> dictionaries.  (There's no OOP at all in this course.  Students don't
>> even write ls.append(...).  They write list.append(ls, ...)).
>
> Nitpickery... there *is* OOP in the course, they just don't know it.
>
> Long long ago (over 20 yrs now) I developed a Python course for a
> commercial training provider, and in it I claimed one of the great 
> things about Python was it supported all kinds of object oriented
> programming techniques, but you could also use it without doing
> anything object oriented. If I wrote a course now, I'd never make that
> claim, because everything you do in Python is pretty much object
> oriented.
>
>>>> x = list()
>>>> type(x)
> <class 'list'>
>>>> dir(x)
> ['__add__', '__class__', '__class_getitem__', '__contains__',
> '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', 
> '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__',
> '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', 
> '__iter__', '__le__', '__len__', '
> __lt__', '__mul__', '__ne__', '__new__', '__reduce__',
> '__reduce_ex__', '__repr__', '__reversed__', '__rmul__',
> '__setattr__', '__setitem__', '__sizeof__', '__str__',
> '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend',
> 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
>
> list is a class and it has methods... it's "object-oriented"!
>
>
> Even if you do
>
> x = 2 + 3
>
> you're actually creating an integer object with a value of 2, and
> calling its add method to add the integer object with the value of 3
> to it. The syntax hides it, but in a way it's just convenience that it
> does so...
>
>>>> 2 + 3
> 5
>>>> x = 2
>>>> x.__add__(3)
> 5
>
>
> sorry for nitpicking :)  But... don't be afraid of letting them know
> it's OOP, and it''s not huge and complex and scary!

I totally agree with you but I didn't know that even numbers were like
that in Python.  In fact, I still don't quite believe it...

>>> 2.__add__(3)
SyntaxError: invalid syntax

But then I tried:

>>> (2).__add__(3)
5

Now I do believe it! :-)  Awesome.  I had no idea.

(*) More opinions

So, yeah, the idea of a course like that is to try to simplify the world
to students, but it totally backfires in my opinion.  There is so much
syntax to learn, so many little details...  We spend the entire semester
discussing these little details.

I posted here recently a study of the semantics of slices.  When I
finally got it, I concluded it's not very simple.  The course introduces
a few examples and expects students to get it all from these examples.
I would rather not introduce slices but teach students enough to write
procedures that give them the slices.  The slices are the fish; learning
to write the procedures is the know-how.  (I'm fine with even teaching
them how to write procedures to add or subtract numbers [and the rest of
arithmetic], although none of them would find mysterious what is the
meaning of arithmetic expressions such as 3 + 6 - 9, even taking
precedence of operators into account.  That's syntax they already know.
If we teach them the syntax of procedures, we could be essentially done
with syntax.)