[Edu-sig] Python for Beginners

[John Posner]

> 
> I think in an Intro to Programming course featuring Python or 
> not, it'd make sense to talk a lot ... 

I suggest talking a little, not a lot. Your note about "Let" is good. How
about just a short explanation that in algebra (the context in which most
students are likely to have encountered the concept of a variable), we make
*declarations of truth*:

   x = 12 + y
   the value of x IS EQUAL TO the value of the expression "12 + y"

... whereas in computer programming, we *give instructions* to the computer:

   x = 12 + y
   LET the value of x BE EQUAL TO the value of the expression "12 + y"

> ... about this new use of the 
> equality symbol ( = ) and how language designers have felt 
> about it (suspicious in some cases).

I suspect that students in an Intro to Programming course couldn't care less
about what the language designers thought. Language comparison in an intro
course is more likely to be confusing than enlightening. How many high
schools teach French and Spanish in the same course?

> Post-its also have this problem of needing to be physically 
> connected to things (that's the hallmark of post-its, they 
> stick to stuff).

You can't convince me that John Zelle's sticky note metaphor is anything
other than *fabulous*: they're different from objects, but are attached to
objects; they can be easily removed from one object and attached to another;
they can be destroyed without affecting the objects to which they were
attached.

My only complaint is that John doesn't use the metaphor *more* in his
textbook! :-)

> When I go y = x in Python, it's like x emailing a web address 
> to y.

Um, it's *way* more like attaching a sticky note to a physical object.

> (what true beginners are likely familiar with, given 
> at least minimal GUI-based file management experience)

That's a "true beginner"?

> Either way x = y might come across as "static through time" 
> in some way, whereas in many computer languages (I'm not 
> saying all), we're talking about a quick happening, a few 
> nanoseconds or clock cycles, then it's all over.

Nope, the sticky note remains attached to the object for a considerable
period -- until it's removed from that object and placed on another one.

[ ... or until the naming scope disappears. John Zelle, do you include this
situation in your sticky-note metaphor? Could sticky notes *of a particular
color* or "with a particular shape* indicate the names in a particular
scope? ]

-John Posner