Scheme style and Python style [was: Re: Typed Python?]

François Pinard pinard at iro.umontreal.ca
Mon Jul 5 06:10:46 CEST 2004


[Ville Vainio]
> [Chain Lube]

> > The code is much better structured in Scheme than in Python. It is a
> > big mistake to assume that Python displays any readability.

> With all due respect, someone that thinks [...]

Flamatory comments are not really my bag. :-)

But as someone who much liked both Scheme and Python, let me stress a
few aspects where Python attracted me more than Scheme.

The most important one is the bulk of library code which comes standard
with Python, but which has to be collected or rewritten in Scheme, not
being part of the standard.

Another is that, despite Scheme attempts to be minimalist (something
that I much like), Python is -- or at least once was! :-) -- more on the
side of having only one way of doing things.  Two examples come to mind.

Scheme has three ways to write a conditional statement: `(cond ...)',
`(if ...)' and `(case ...)'. All have virtues and drawbacks, and I often
switch between the three, depending on my code, and the edits I do on my
code, so it stays best at all time.  This is annoying.

Scheme has many ways for looping while changing local variables, some
of which are less nice and which I did not use much, I'm not even
discussing them.  The `(let loop ...)' construct is useful for writing
tail-recursive loops without creating a flurry of little separate
functions, but it is often clearer writing destructive `(set! ...)'
instead of always being tail-recursive, even if tail-recursivity
often yields more efficient compilation.  When you mix assignment and
tail-recursion, the amount of solutions for a piece a code is near
exponential in the number of variables.  I found this annoying, too.

Bindings, conditionals and loops are very basic and ubiquitous in any
programming language, and Python got these relatively simpler than
Scheme.  Scheme may be minimalist overall, but because of the frequency
of the above constructs in a program, the minimalism is not so apparent.

P.S. - On the other side, in those rare circumstances one needs
continuations, Scheme offers them very easily, while there are rather
painful to simulate in standard Python.  Also, there once was a notable
distance between Scheme and Python about lazy evaluation and closure
construction, but more recent versions of Python offer fairly tractable,
almost easy approaches for such things.

-- 
François Pinard   http://www.iro.umontreal.ca/~pinard




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