Python's "only one way to do it" philosophy isn't good?

[WaterWalk]

I've just read an article "Building Robust System" by Gerald Jay
Sussman. The article is here:
http://swiss.csail.mit.edu/classes/s...st-systems.pdf

In it there is a footprint which says:
"Indeed, one often hears arguments against building exibility into an
engineered sys-
tem. For example, in the philosophy of the computer language Python it
is claimed:
\There should be one|and preferably only one|obvious way to do
it."[25] Science does
not usually proceed this way: In classical mechanics, for example, one
can construct equa-
tions of motion using Newtonian vectoral mechanics, or using a
Lagrangian or Hamiltonian
variational formulation.[30] In the cases where all three approaches
are applicable they are
equivalent, but each has its advantages in particular contexts."

I'm not sure how reasonable this statement is and personally I like
Python's simplicity, power and elegance. So I put it here and hope to
see some inspiring comments.

[Gabriel Genellina]

En Sat, 09 Jun 2007 02:49:03 -0300, WaterWalk <to********@163 .com>
escribió:

I've just read an article "Building Robust System" by Gerald Jay
Sussman. The article is here:
http://swiss.csail.mit.edu/classes/s...st-systems.pdf

In it there is a footprint which says:
"Indeed, one often hears arguments against building exibility into an
engineered sys-
tem. For example, in the philosophy of the computer language Python it
is claimed:
\There should be one|and preferably only one|obvious way to do
it."[25] Science does
not usually proceed this way: In classical mechanics, for example, one
can construct equa-
tions of motion using Newtonian vectoral mechanics, or using a
Lagrangian or Hamiltonian
variational formulation.[30] In the cases where all three approaches
are applicable they are
equivalent, but each has its advantages in particular contexts."

I'm not sure how reasonable this statement is and personally I like
Python's simplicity, power and elegance. So I put it here and hope to
see some inspiring comments.

I think the key is the word you ommited in the subject: "obvious". There
should be one "obvious" way to do it. For what I can remember of my first
love (Physics): if you have a small ball moving inside a spherical cup, it
would be almost crazy to use cartesian orthogonal coordinates and Newton's
laws to solve it - the "obvious" way would be to use spherical coordinates
and the Lagrangian formulation (or at least I hope so - surely
knowledgeable people will find more "obviously" which is the right way).
All classical mechanics formulations may be equivalent, but in certain
cases one is much more suited that the others.
--
Gabriel Genellina

[Terry Reedy]

"WaterWalk" <to********@163 .comwrote in message
news:11******** **************@ r19g2000prf.goo glegroups.com.. .
| I've just read an article "Building Robust System" by Gerald Jay
| Sussman. The article is here:
|
http://swiss.csail.mit.edu/classes/s...st-systems.pdf
|
| In it there is a footprint which says:
| "Indeed, one often hears arguments against building exibility into an
| engineered sys-
| tem. For example, in the philosophy of the computer language Python it
| is claimed:

For him to imply that Python is anti-flexibility is wrong. Very wrong..
He should look in a mirror. See below.

| \There should be one|and preferably only one|obvious way to do
| it."[25] Science does
| not usually proceed this way: In classical mechanics, for example, one
| can construct equa-
| tions of motion using Newtonian vectoral mechanics, or using a
| Lagrangian or Hamiltonian
| variational formulation.[30] In the cases where all three approaches
| are applicable they are
| equivalent, but each has its advantages in particular contexts."

And in those contexts, one would hope that the method with advantages is
somehow the obvious way to do it. Otherwise beginners might become like
Buriden's ass.

So I dispute that science is as different as he claims. And I do not see
any real value in the statement in that I do not see it saying anything
useful to the reader, at least not in this snippet.

| I'm not sure how reasonable this statement is and personally I like
| Python's simplicity, power and elegance. So I put it here and hope to
| see some inspiring comments.

How much has Mr. Sussman actually programmed in Python and what actual
problems did he find with the *implementation * of the philosophy? Without
something concrete, the complaint is rather bogus.

But here is what I find funny (and a bit maddening): G. J. Sussman is one
of the inventers of the Lisp dialect Scheme, a minimalist language that for
some things has only one way to do it, let alone one obvious way. Scheme
would be like physics with only one of the three ways. After all, if they
are equivalent, only one is needed.

For example, consider scanning the items in a collection. In Python, you
have a choice of recursion (normal or tail), while loops, and for
statements. For statements are usually the obvious way, but the other two
are available for personal taste and for specially situations such as
walking a tree (where one might use recursion to write the generator that
can then be used by for loops. In scheme, I believe you just have
recursion. Since iteration and recursion are equivalent, why have both?

Terry Jan Reedy

[James Stroud]

Terry Reedy wrote:

In Python, you have a choice of recursion (normal or tail)

Please explain this. I remember reading on this newsgroup that an
advantage of ruby (wrt python) is that ruby has tail recursion, implying
that python does not. Does python have fully optimized tail recursion as
described in the tail recursion Wikipedia entry? Under what
circumstances can one count on the python interpreter recognizing the
possibility for optimized tail recursion?

James
=====

Disclaimer: Mention of more than one programming language in post does
not imply author's desire to begin language v. language holy battle. The
author does not program in [some or all of the other languages mentioned
aside from the language topical to the newsgroup] and has no opinions on
the merits or shortcomings of said language or languages.

=====

[Cousin Stanley]

....
In scheme, I believe you just have recursion.
....

Cousin TJR ....

I'm a total scheme rookie starting only about 3 days ago
and one of the mechanisms I went looking for was a technique
for iteration ....

Found in the scheme docs about iteration supplied
via the reduce package ....

"Iterate and reduce are extensions of named-let
for writing loops that walk down one or more sequences
such as the elements of a list or vector, the characters
read from a port, or arithmetic series .... "

The following scheme session illustrates a trivial example ....

, open reduce

( define ( list_loop this_list )

( iterate loop
( ( list* this_item this_list ) ) ; iterate expression
( ( new_list '( ) ) ) ; state expression
( loop ( cons ( * 2 this_item ) new_list ) ) ; body expression
( reverse new_list ) ) ) ; final expression
; no values returned

>
( define L '( 1 2 3 4 5 ) )

; no values returned

>

( define result_i ( list_loop L ) )
; no values returned

>
result_i

'(2 4 6 8 10)

>

However, just as in Python the map function
might be both easier to code and more readable
in many cases ....

( define ( x2 n ) ( * 2 n ) )

; no values returned

>
( define result_m ( map x2 L ) )

; no values returned

>
result_m

'(2 4 6 8 10)

Note ....

No lambdas in my scheme code either .... ;-)
--
Stanley C. Kitching
Human Being
Phoenix, Arizona
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[Bjoern Schliessmann]

Gabriel Genellina wrote:

For what I can
remember of my first love (Physics): if you have a small ball
moving inside a spherical cup, it would be almost crazy to use
cartesian orthogonal coordinates and Newton's laws to solve it -
the "obvious" way would be to use spherical coordinates and the
Lagrangian formulation (or at least I hope so

Yep, that's right.

- surely knowledgeable people will find more "obviously" which is
the right way).

No, this case is IMHO almost classical. Movement with planar
constraints can be solved quite easy using Lagrange.

All classical mechanics formulations may be equivalent, but
in certain cases one is much more suited that the others.

Or: Lagrange is the only obvious way to describe movement with
constraints.

Regards,
Björn

--
BOFH excuse #80:

That's a great computer you have there; have you considered how it
would work as a BSD machine?

[Kay Schluehr]

On Jun 9, 12:16 pm, James Stroud <[e-mail] la.eduwrote:

Terry Reedy wrote:

In Python, you have a choice of recursion (normal or tail)

Please explain this. I remember reading on this newsgroup that an
advantage of ruby (wrt python) is that ruby has tail recursion, implying
that python does not.

Proof by rumour? You can use first class continuations in Ruby to
eliminate tail calls in and define higher order function wrappers
( like Python decorators ). But I wouldn't call this "fully
optimized".

Does python have fully optimized tail recursion as
described in the tail recursion Wikipedia entry?

No.

[Terry Reedy]

"James Stroud" <js*****@mbi.uc la.eduwrote in message
news:E5******** *******@newssvr 17.news.prodigy .net...
| Terry Reedy wrote:
| In Python, you have a choice of recursion (normal or tail)
|
| Please explain this.

I am working on a paper for Python Papers that will. It was inspired by
the question 'why doesn't Python do tail-recursion optimization'.

tjr

[Terry Reedy]

"Cousin Stanley" <co***********@ hotmail.comwrot e in message
news:11******** ******@sp12lax. superfeed.net.. .
| In scheme, I believe you just have recursion.

I was referring to the original mimimalist core language developed by Guy
and Sussman and as I remember it being used in the original edition of SICP
(see Wikipedia). I also remember statements explaining (truthfully) that
builtin iteration is not needed because it can be defined in terms of tail
recursion, which in Scheme is required to be optimized to be just as space
efficient.

I see in Wikipedia that Scheme has do loops (all versions?), but I do not
know if that was original or added. If the former, it was de-emphasized.
Hence my belief, even if mistaken.

| Cousin TJR ....
|
| I'm a total scheme rookie starting only about 3 days ago
| and one of the mechanisms I went looking for was a technique
| for iteration ....
|
| Found in the scheme docs about iteration supplied
| via the reduce package ....

Right. An add-on library package, not part of the core;-)

In Python, modules can add functions (and classes, etc), but not statement
syntax, so adding while statements defined in terms of recursion is not
possible.

Scheme is quite elegant and worth learning at least the basics of. My only
point was that Sussman is an odd person to be criticizing (somewhat
mistakingly) Python for being minimalist.

tjr

[John Nagle]

Bjoern Schliessmann wrote:

Gabriel Genellina wrote:

>>For what I can
remember of my first love (Physics): if you have a small ball
moving inside a spherical cup, it would be almost crazy to use
cartesian orthogonal coordinates and Newton's laws to solve it -
the "obvious" way would be to use spherical coordinates and the
Lagrangian formulation (or at least I hope so

Having actually solved that problem in simulation, I can report
that it's easier in Cartesian coordinates. I used to use this as
a test of Falling Bodies, one of the first physics engines that
really worked on the hard cases.

Spherical coordinates seem attractive until you have to deal
with friction between the ball and cup. The ball is rotating, too,
and may be slipping with respect to the cup. Then the simple
Physics 101 approach isn't so simple any more.

John Nagle
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