tough-to-explain Python

Bearophile bearophileHUGS at lycos.com
Tue Jul 7 23:46:01 CEST 2009


kj, as Piet van Oostrum as said, that's the difference between mutable
an immutable. It comes from the procedural nature of Python, and
probably an explanation of such topic can't be avoided if you want to
learn/teach Python.

Lot of people think that a language where everything is immutable is
simpler for newbies to understand (even if they have to learn what
higher-order functions are). That's why some people think Scheme or
other languages (even Clojure, I guess) are better for novices (Scheme
has mutability, but you can avoid showing it to newbies).

Some people say that languages that mostly encourage the use of
immutable data structures (like F#, Clojure, Scala and many other less
modern ones) help avoid bugs, maybe for novices too.

On the other hand, it's hard or impossible to actually remove
complexity from a system, and you usually just move it elsewhere. So
other things will become harder to do for those novices. I have no
idea if for the average novice it's simpler to learn to use a
immutables-based language instead of a mutables-based one (it can also
be possible that some novices prefer the first group, and other
novices prefer the second group).

>From what I have seen lot of students seem able to learn Python, so
it's not a bad choice.

Python isn't perfect, and in *many* situations it is pragmatic, for
example to increase its performance. Generally for a novice programmer
running speed is not important, but it's important to have a really
coherent and clean language. I've personally seen that for such people
even Python looks very "dirty" (even if it's one of the less dirty
ones).

For example a novice wants to see 124 / 38 to return the 62/19
fraction and not 3 or 3.263157894736842 :-)

People may be able to invent a clean and orthogonal language that's
easy to use and has very few compromises, fit for newbies. But this
language may be very slow, not much useful in practice (who knows?
Maybe there's a practical niche even for such very high level
language), and it doesn't teach how to use lower level languages like
C :-)

Today I think there are no languages really fit for teaching. Python
is one of the few fit ones, but it's getting more and more complex as
time passes because it's getting used in more and more complex real
world situations (a language fit for newbies must not have abstract
base classes, decorators, etc). D language is too much complex for a
newbie. Java is not too much bad, but it's requires to write too much
code, it's too much fussy (semicolons at the end of lines? Newbies say
that the computer is an idiot when it refuses code just because
there's a missing useless semicolon!), and it misses some necessary
things (first class functions! Damn). A nice language like Boo running
on the Mono VM seems another option :-)

In the past Pascal was good enough, but I think it's not good enough
anymore. The problem is that teaching is a niche activity (even if a
very important one). PLT Scheme is one of the few environments (beside
Squeak, Python itself, and little more) that look refined and
implemented well enough for such purpose.

See you later,
bearophile



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