some problems for an introductory python test

[Hope Rouselle]

Chris Angelico <rosuav at gmail.com> writes:

> On Wed, Aug 11, 2021 at 4:18 AM Hope Rouselle <hrouselle at jevedi.xotimo> wrote:
>>
>> 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
>
> Yeah, that's because "2." looks like the beginning of a float.
>
>> But then I tried:
>>
>> >>> (2).__add__(3)
>> 5
>>
>> Now I do believe it! :-)  Awesome.  I had no idea.
>
> You can also do it this way:
>
>>>> x = 2
>>>> x.__add__(3)
> 5
>
> But don't teach this; it ignores several problems. 

I wouldn't.  This is all Python-stuff.  The course chooses a language
like Python, but it is not trying to teach Python --- it is trying to
teach computer programming, that is, strategies in high-precision.

[...]

>> (*) 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.
>
> Agreed, and if you try to teach all the syntax, you're inevitably
> going to get bogged down like that.

Indeed.

>> 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.)
>
> A language like Python is useful, not because every tiny part of it is
> easy to explain, but because the language *as a whole* does what is
> expected of it. Toy languages are a lot easier to explain on a
> concrete level (look up Brainf*ck - it has very few operations and
> each one can be very simply defined), and that might be tempting in
> terms of "hey, we can teach the entire language in ten minutes", but
> they're utterly useless for students.

Sure.  I would never use a toy language like that.  I think we need a
compromise --- some syntax, but not too much; in fact, just a little bit
of syntax.  For instance, could we do away with slices?  We could.  If
we learn one way of looping, we can build slices with procedures.  This
is a good opportunity in fact --- it will show students how slices
really work and how to get what they want with it.  (Then towards the
end we could give out a lecture for anyone interested in Python ---
``while we didn't show you how Pythonists usually write, here's a few
things that Pythonists would do that we didn't do in this course...'')

> Instead, my recommendation would be: Entice students with power.
> Pretend you're teaching some aspect of magic at a wizards' school and
> make sure your students feel massively OP. Sure, they might not
> understand what makes those cantrips work, but they know that they DO
> work. You can have students casting print calls left and right, doing
> complex incantations with list comprehensions, and even defining their
> own classes, all without ever worrying about the details of how it all
> works. Then once the "wow" is achieved, you can delve into the details
> of how things actually function, transforming progressively from
> "wizardry" to "science".

I really like that, but I would predict that, in a typical university,
professors are not really willing to go that way.  Everything has to be
extremely simple --- and a mess is made in trying to achive that.  (In a
sense, professors are all failing terribly.  They're lucky that nobody
is giving them a grade based on how effective they are as evidenced by
the facts, however such thing would be done in practice if one were to
take it seriously.)

> And to be quite frank, a lot of code IS magic to most programmers.

Definitely.  You guys are showing me so much Python here that I've never
seen --- which I expect, because I'm only paying attention at Python now
since I'm conducting students through a course that's using it.  (I
admire the language, but I never used it in any project on my own.  I
probably would if I were not in love with other similar technology.)

> Which isn't a problem. Do you REALLY need to understand how your CPU
> does register renaming in order to benefit from it? Or do you need to
> know every detail of the TCP packet header before using the internet?
> Not likely. 

Not at all.  (Although, of course, we like to know these stuff.)

> Those details hide away under the covers, and we make happy use of
> them. There's infinite knowledge out there, and you - and your
> students - are free to dip into exactly as much as you're comfortable
> with.

``A man after my own heart.''