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Learn a scripting language besides Python [closed]

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Someone told me once, that programmers tend to learn one scripting language properly and ignore or dislike other scripting languages. Do you have similar experiences?
I'm using Python as my choice for scripting for few years, however, I'm sure that there are many existing and emerging languages that could impress the Pythonistas. Can you recommend scripting languages that would be interesting and useful to learn besides of Python?

Look, Python pretty much has all you need (in my opinion) for application programming. You can write anything from a protocol stack to YouTube, from media players to 3D games and graphics and you get excellent performance.
It occupies the same niche as some of these other mentioned languages:
C, you have access to almost all of the useful C/C++ libraries. The only reason I would pick to write something in C over Python is because I needed the performance gain. Even then, I would probably prototype it in Python first; it's much easier to revise your design when your application is written in Python.
Ruby, there is no good reason to ever use Ruby instead of Python.
Perl, it's great for some particular kinds of tasks, but if you're a fan of consistent, readable and sane programming styles you will hate looking at about 95% of existing Perl code. I don't know if this is because the people who program in Perl tend to be (in my experience) sys admins first and programmers second, or because Perl has a design philosophy that allows for multiple distinct ways to achieve the same effect.
Given that, I would say that if you are going to learn another language, make sure it gives you the ability to do something new. There are two scripting languages that I would recommend for you to learn:
Bash, what a joy it is to manipulate your filesystem with a combination of for loops and pipes. Bash programming doesn't give you more than what you can already do with Python, but if you are a *nix user you will experience great gains in your daily productivity.
Javascript, being able to write browser-based applications is a useful skill and almost definitely the way most applications will be done in the future. The Javascript/browser environment is set to gain a whole host of capabilities in the coming few years, from audio manipulation to OpenGL graphics, and some very fast engines are either in the works or already available (like V8, which powers the Chrome browser and compiles Javascript to native byte code.) Have you seen Quake2 ported to WebGL?
My answer basically boils down to this: first, learn languages that are useful.

Ruby - what it enables and does with blocks is really interesting, and quite foreign to python based programming
Erlang - the functional language has a lot of interesting examples and it will definitely make your head work differently afterwards (in a good way)
Javascript - yes, I'm serious. ALthough there's a fair number of grips to be had with this prototype language, it does some really interesting things with that prototyping and just slightly differently than Ruby and/or Python. And a ton of folks are pouring big money into making Javascript a outstandingly fast scripting language.

I would recommend learning Haskell and a dialect of Lisp such as Scheme or Common Lisp, if you master either of those you'll gain insight into how things are accomplished with the functional paradigm and it'll help out your Python as well.
Here are some languages categorized by paradigms I'd learn:
Imperative/Procedural languages:
C
Functional paradigm languages:
Haskell
Common Lisp/Scheme
Similar object oriented languages:
Ruby
ECMAScript
Other:
Perl
I would advise you to stay away from PHP unless you really need the work. You would probably want to run back to Python.

Scripting languages are so similar that the marginal benefit of moving from one scripting language to another is usually low. So it's unsurprising that people wouldn't bother to learn more than one. Nevertheless, in my career I have passed through times when my main scripting language (in roughly chronological order) was
Awk
Tcl
Icon
Ksh
Lua
I also used Perl and Python but never found them enough better to be worth switching to.
If you want to check out another scripting language, I recommend Lua, because
It's powerful and remarkably simple, having the best power-to-weight ratio of all languages named here.
Like Tcl it was designed from the beginning to incorporate C code seamlessly. This facility works extremely well and greatly extends the range of problems for which it is useful (see Adobe Lightroom, World of Warcraft, Garry's Mod, CHDK).
The implementation is highly performant and brilliantly engineered. If you want to learn something about how languages are implemented, it will repay careful study.
If, however, your goal is to learn a new language to expand your mind, learn something else besides a scripting language. For example, learn Haskell and pick up some mind-blowing ideas (many stolen from the same sources that Guido stole from), or learn C and really understand exactly what's happening on the hardware.

The only relatively unbiased answer you can really look for is probably statistical, and you would still have to account for the natural tendency of people to follow the path of least resistance once one is found or carved.
How many people learnt Python to a decent level, found the language resonates with the way they want to work, then move to something else because the language or the ecosystem, or both, don't support their needs?
I'd say probably a single digit percentage of the educated userbase, wouldn't be surprised if it amounted to less than 5%.
Unless you have work related prospects that involve a different language, or you need to move sideways for similar reasons, I'd say you're probably best off learning something complimentary to Python rather than similar or equivalent.
C++ for low-level or computationally intensive tasks, CUDA if your field can take advantage of it (med-viz, CGI etc.), whatever flavour of shell/sysadmin oriented scripting and hacks float where you work (bash, tcl, awk or whatever else) and so on.
Personally the reason I haven't bothered past a first glance with ruby, php, or a number of other languages is simply that it's better ROI to keep working on my python skills than picking up something that offers mostly the same qualities just in different forms.
If you really want to learn something else for the sake of opening your mind up a bit, and want to stick to "scripting", then LUA was an interesting toy for me for a while, mostly for the ridiculous performance you can squeeze out of a relatively easy integration process, and because it is a rather different set of tracks compared to Python. That, and the fact WoW plugins had to be written in LUA ;)

I'll give an honest answer from my perspective.
No.
Having started scripting using batch, bash, and Perl, discovering Python was discovering precisely what I'd want from a scripting language (and more, but that's off topic). It integrates with familiar Unix interfaces, is modular, doesn't force any particular paradigm, cross platform and under active development. The same can be said of no other scripting language I know of.
The only other scripting languages I'd consider using is Lua or Scheme, for their smaller footprints and suitability for embedding, Python can be a little hefty. However they're hardly suitable for the more general purpose shell and other forms of scripting.
Update0
I just noticed mentions of Ruby and PHP in other answers, these both slipped my mind, because I'd never consider using them. Ruby is slower and not quite as popular, and PHP is more C/Perl like, with flatter interfaces, which comes with performance boons of its own. Using these alternatives to Python is a matter of taste.

To answer your first question: Do people learn one language and then ignore or dislike others?
Well, if you know one language well, you will need to see great advantages to move to another.
I started out using perl and eventually thought that there must be easier way to do some things. I picked up python and stopped using perl almost at once.
A little while later I thought I'd try ruby and learned a bit about that. The advantages over using python weren't big enough to switch, so I decided to stick with python. If I had started out using ruby, I'd probably be using that still.
If you are using python, I don't think you will easily find another scripting language that will win you over.
On the other hand, if you learn functional programming, you will probably learn a few new things, some of them will even be useful in your python programming, since a few things in python seems to be inspired by functional programming and knowing how to use them will make you a better programmer in general and a better python programmer too.

Learn a Lisp. Whether it's "scripting" or not, Eric Raymond had the right of it when he wrote:
"Lisp is worth learning for the
profound enlightenment experience you
will have when you finally get it;
that experience will make you a better
programmer for the rest of your days,
even if you never actually use Lisp
itself a lot."
The programming paradigm needed to be highly effective in Lisp is sufficiently unlike what you use with Python day-to-day that the perspective it gives is very, very much worth it.
And within Lisps, my choice? Clojure; like other Lisps, its macro system gives you capabilities comparable (actually superior) to the excellent metaprogramming in Python, but Clojure in particular has a focus on batteries-included practicality (and an intelligent, opinionated design) which will be familiar to anyone fond of GvR's instincts. Moreover, Clojure's strengths are extremely disjoint from Python's -- in particular, it shines at highly-multithreaded, CPU-bound concurrent programming, which is one of Python's weaknesses -- so having both in your toolbox increases the chance you'll have the right tool when a tricky job comes along.
(Is it scripting? In my view, that's pretty academic these days; if you have a REPL where you can type code and get an immediate response, modify the state of a running program, or experiment with an API, I see a language as "scripting" enough).

I would learn a statically typed language with very powerful type expression capabilities and awesome concurrency.
One of the following would be a good choice (in order of my preference):
Scala
F#
Haskell
Ocaml
Erlang
Typed languages like the above make you think different. Also these languages have REPLs so they can be used as a scripting language although truthfully I'm not really sure what the definition is of "scripting" language is.
Python is missing good concurrency builtin to the language so knowing how to deal with concurrency for many python programmers is a challenge.
I have found that strongly typed languages scale better for big projects for many reasons:
Because types are so important they become an invaluable way to communicate the problem
Refactoring in these languages is much much easier.
Automatic Serialization is sometimes easier too (although for Haskell thats less true).
A lot less time spent on writing assertions on type checking.
Browsing the code is easier because most IDEs will allow you click on and go to different types

I'm actually learning Scala after Python. From "Programming in Scala":
The name Scala stands for “scalable language.” The language is so named because it was designed to grow with the demands of its users. You can apply Scala to a wide range of programming tasks, from writing small scripts to building large systems.
Integration of object-oriented and functional programming inside the language with expressive strong static type system is interesting by itself. And yes, you can use Scala as scripting language. I feel uncomfortable coding in languages with dynamic typing discipline so Scala seems to be a good alternative. Besides its complexity at the initial learning stage.
If you satisfied with dynamic typing discipline take a look at the roots. Smalltalkof course. Try Squeak with Squeak by Example companion book or its open-source fork Pharo with Pharo by Example book for the start.

Ruby/Groovy/Perl if you'd like to stick to traditional scripting practices.
Otherwise I'd heartily recommend you Clojure and Scala - two of the more innovative programing languages of the past few years.

If you are already familiar with Python, you are unlikely to find something compelling in the same niche, although Ruby does have a very strong and vocal following that seems to like it very much. Perhaps you should consider a scripting language that fills a different role, such as BASH shell script for quick, simple scripts that don't need the complexity of Python or JavaScript which runs in the browser.

I can't say that I agree with wiping Ruby off the map... Ruby fixed every problem that perl had as far as syntax goes... I loved Python first but let ruby get a little more mature and it will get in the the fray more and more... Why do I support Ruby strongly? just step away from python for a few months and then give Ruby a chance... I was a Ruby hater when I was a python guy. But I can't hardly stand to use python at this point. One day someone is gonna clean up the GC and toss in some native threads and everybody better watch out.
off the rant, Python is a full featured, not just good, Great Language... Perl... what a mess... I don't know how Perl can look at itself in the mirror standing next to any other mainstream scripting language... PHP is much prettier... At least Perl is fast, right...(CPAN never hurt it either) if Speed is the real issue there are other interpreters that juice it up a bit... Jython, jRuby, PyPy... the list goes one, screw Bash...

From interpeted to native code: "dynamic" languages compiler support

First, I am aware that dynamic languages is a term used mainly by a vendor; I am using it just to have a container word to include languages like Perl (a favorite of mine), Python, Tcl, Ruby, PHP and so on. They are interpreted but I am interested here to refer to languages featuring strong capability to support the programmer efficiency and the support for typical constructs of modern interpreted languages
My question is: there are dynamic languages can be compiled efficiently in native executable code - typically for Windows platforms? Which ones? Maybe using some third part ad-hoc tools? I am not talking about huge executables carrying with them a full interpreter or some similar tricks nor some smart module able to include its own dependances or some required modules, but a honest, straight, standard, solid executable code.
If not, there is some technical reason inhibiting the availability of such a best-of-both-world feature?
Thanks!
Daniel

I think you're operating under a misunderstanding: These executables aren't huge because they just lump the interpreter in there, they're huge because the whole runtime is in there.
On Windows, most of your runtime is already installed, so you don't have to ship it. You think your program is small, but a quick look at the virtual memory mappings will tell you that even a small "hello-world" type program written in C is a couple megabytes big.
That's just how big useful runtimes are.
If you really want to keep your ship-size small, your only choice is to use the runtimes that are already there, and that means C/C++ and (recently) dot-net.
If you really can't swallow the runtime, Forth is as small as it gets.
The best, most aggressive dynamic languages with the best compilers for Windows are the commercial Lisps. They do a lot of inlining and pruning when producing executables, so you end up shipping only what you use. They are still 1.5x to 5x larger than C/C++ programs.
As far as languages that you know: Perl is as fat as they get. ActiveState has perlapp which I'm sure you're already aware of, but you dismissed because of it's size. Revisit it if you can.
Now, to answer your question (is) there is some technical reason inhibiting the availability of such a best-of-both-world feature?: Yes.
Perl cannot be statically analyzed (proof), which means there's no way for a perl compiler to tell what can be discarded. That means every part of Perl's runtime needs to be available to your program becuase there's no way for your program to indicate what parts can be discarded.
That means that getting a smaller executable is equivalent to getting a smaller runtime, and you should be comfortable accepting that if the perl developers knew how to make the perl runtime smaller without discarding any features, they'd probably do it.
If you are willing to write in a strict subset of Python or PHP, these languages can be analyzed. Shed Skin and HipHop-php are pretty good, but they're still quite large, and they don't support all of Pythons and PHP's features which means that some modules will simply not work. To my knowledge, nobody has implemented pruning for either of these languages (most of the focus in these compilers is in improving their lackluster performance) and it may be another decade or more before anyone bothers, however these still will be the restrictions you have to accept when doing this sort of thing.

The PyPy project does what you describe for a fairly complete subset of Python.
In the general case, this is a very hard problem to solve, largely due to the very attributes that make these languages "dynamic": late binding, weakly-typed variables, data structures and containers, eval facilities, a fuzzy divide between programming and meta-programming, etc. But a lot of effort is being poured into it, such as the JavaScript JIT-compiler projects listed here.

Shed Skin is an experimental (and restricted) Python-to-C++ compiler that can do what you describe. As Marcelo indicates above with PyPy, there are limitations on what you can compile with Shed Skin, but if you are willing to accept the restrictions, you can achieve large speedups.

Standardizing a Release/Tools group on a specific language

I'm part of a six-member build and release team for an embedded software company. We also support a lot of developer tools, such as Atlassian's Fisheye, Jira, etc., Perforce, Bugzilla, AnthillPro, and a couple of homebrew tools (like my Django release notes generator).
Most of the time, our team just writes little plugins for larger apps (ex: customize workflows in Anthill), long-term utility scripts (package up a release for QA), or things like Perforce triggers (don't let people check into a specific branch unless their change description includes a bug number; authenticate against Active Directory instead of Perforce's internal passwords). That's about the scale of our problems, although we sometimes tackle something slightly more sizable.
My boss, who is reasonably technical, has asked us to standardize on one or two languages so we can more easily substitute for each other. He's advocating bash scripts and Perl, due to their universality and simplicity. I can see his point--we mostly do "glue", so why not use "glue" languages rather than saddle ourselves with something designed for much larger projects? Since some of the tools we work with are Java-based, we do need to use something that speaks JVM sometimes. (The path of least resistance for these projects is BeanShell and Groovy.) I feel a tremendous itch toward language advocacy, but I'm trying to avoid saying "We should use Python 'cause I like it and Perl is gross."
Instead, I'm trying to come up with a good approach to defining our problem set: what problems do we solve with scripts? Would we benefit from a library of common functions by our team, or are most of our projects more isolated? What is it reasonable to expect my co-workers to learn? What languages give us the most ease of development and ease of modification?
Can you folks suggest some useful ways to approach this problem, both for my own thinking process and to help me facilitate some brainstorming among my coworkers?

Two points:
"Eww Perl gross" is somewhat of an urban legend. You can write great clean self-documenting code in Perl, and your can write write-only code in pretty much any language. It's a property of a developer, not a language.
Just because you're writing glue code, doesn't mean the code has to suck like some glue hacks tend to be.
From many threads comparing Perl vs Python on SO, it appears to me that Perl's CPAN is more expansive than Python's repository, but I have no experience with Python and can't substantiate with real comparison.
BUT, one thing I do know. After 5 seconds search, CPAN has a JIRA module. Whether that's a good factor for you or not, that's up to you.

Google standardized on Python for such tasks (and many more) a bit before I joined the company; as far as I know, huge advantages such as Python's great implementations on the JVM and .NET didn't even play a role in the decision -- it was all about readability. At the time (and to some extent, even now) the theory at Google was that every engineer must be able, at need, to tweak every part of the codebase -- including of course build scripts, spiders (which were in Python at the time), and so forth. Demanding of engineers already proficient in C++ and Java to learn many more "scripting" languages (Python, Perl, Bash, Awk, Sed, and so forth) was simply unconsciounable: one had to be selected. Given that constraint, Python was the clear choice (under other constraints, Perl might also have been -- but I can't see the inevitable mix of Bash, Awk and Sed ever competing on such grounds!_) -- and that's how I ended up working there, a bit later;-).
Given that the overall potential of Python vs Ruby vs Perl vs PHP vs Bash + Awk + Sed vs ... is roughly equal, picking one is clearly a winner -- and Python has clean readability, strong implementations on JVM and .NET as big vigorishes. Seriously, I can only think of Javascript (inevitable for client-side work, now rich with strong implementations such as V8) as a possible "competitor" (unfortunately, JS inevitably carries on a lot of baggage for backwards compatibility -- unless you can use a use strict;-like constraint to help on that, it must be an important downside).

I don't think anyone is going to be able to solve your problem on Stackoverflow. Your choice of tools, methods, and process are much more affected by social constraints, e.g. what your boss wants and what you want, then technical merits. That's not necessarily bad.
The short answer is "Use what is going to be most pleasing to the developers". If everyone likes Python more than Perl, for whatever reason, they are probably going to get more done in Python. If they like Ruby more than Python, it's the same thing.
Some things to evaluate as part of your selection:
What do the developers already know?
What are they most willing to learn?
How much weekly time can your team spend learning new things (e.g. lunch seminars, formal classes, etc)?
What do most people in the community use to work with the tool you need to support? For instance, Fisheye has a Java API, and some REST examples for Perl and Python. If you're writing Fisheye extensions, Java seems to be the win there. If you're merely accessing Fisheye data, any language can use the REST stuff.
What is most of your code base in already? What can you replace and what do you have to continue to support? I find that many companies can't answer this question because every developer seems to add two new technologies they don't tell anyone about. :)
Which platforms do you need to support? Some languages have platform specific issues, and I don't mean just Windows vs. Unix. Do you have legacy hardware you have to support? Does your tool work on that stuff?
How much of the stuff you produce can benefit other parts of the company? What are other teams using?
Do the people advocating one tool know it well enough to be its champion? I ask What are five things he hate about your favorite language? If people can't name five valid things that are wrong with their language or tool, they don't have enough experience with it.
The Longer Answer
People tend to try to reduce this to a technical argument because they are afraid to admit their biases or examine why they think what they think. Your boss might favor bash and Perl because that's what he did a lot of work in when he was getting started. You might like Python because you have a personal affinity for the way Python does things. I like Perl because I like its flexibility and DWIMmery. Like any social situation, different people are going to be attracted to different parts of different things. Just because you like chocolate doesn't make vanilla evil. I could give you lots of good arguments why Perl can be useful, but that doesn't mean that something else can't give you the same value.
What problems do we solve with scripts?
That one you have to answer for yourself. :)
Would we benefit from a library of common functions by our team, or are most of our projects more isolated?
This is most likely a good thing in Python, Perl, Ruby, Java, and almost any other language that you might choose. I think this part of your requirement is language agnostic. No matter which one you choose, you'll probably want to do this.
What is it reasonable to expect my co-workers to learn?
A good developer should be able to work with several different languages at least to an apprentice level. Those languages should include ones that have vastly different assumptions about how people express problems, say, for example, the set { Smalltalk Perl C Lisp Java }.
The best developers I've hired and worked with have always wanted to use the right tool for the job instead of making the job right for the tool. They might have their favorite language, but they didn't grouse (too much) about using a different tool when it made more sense.
Many "developers", however, seem to think that they are getting paid to play with their favorite tool. You need to convert them into people who think they have a toolbox to solve problems that create business value.
And remember, you never stop learning. As a developer you don't have to choose one language then defend it with your life, forsaking all others, in sickness and in health, and so on. Good developers are going to continue to track new technologies and evaluate them for usefulness for their tasks. Just because you choose one tool over another doesn't mean you stop paying attention.
No matter what you choose, someone is going to complain. Don't look for the solution that makes everyone happy. There isn't one, short of getting rid of the developers who aren't happy.
What languages give us the most ease of development and ease of modification?
A skilled practitioner in just about any language will think that his chosen language is the easiest to develop, modify, and maintain. Unskilled practitioners tend to blame the language and the tools for their problems. Some languages have steeper learning curves, and some have bigger payouts. A person's tolerance with immediate gratification is a big factor here.
That being said, different languages have developed different cultures and different toolsets. Perl people tend to like vi or emacs, Ruby people tend to like TextMate, Java people tend to like Eclipse or IntelliJ. That's not always true, but the culture that evolves around the tools are often more important than the technical details of the tool. If your developers like a particular type of tool, they are probably going to like the language that has a culture built around that sort of tool.
Some processes and tools take more time to get used to or require more education, but they can have larger advantages when used properly. Other tools get you started sooner but might not give you a path to bigger and greater things, such as cross-team development. The trick, however, is to not code to the tools so you aren't stuck in any particular toolset.

First, it's important to note that it is very hard to convince someone they're wrong.
He's advocating bash scripts and Perl,
due to their universality and
simplicity
Bash scripts are not simple. The bash programming model is really complex and unfriendly. if statements and expressions, in particular are horrifying.
Perl may or may not be simple.
Bash is universal. Perl, however, is exactly as universal as Python. Python is pre-installed in almost all Linux distributions. So that argument is specious.
The "universality" of bash, Perl and python is exactly the same. The "simplicity", however, is not the same. You won't find it easy to to "prove" or "convince" anyone of this once they've already pronounced Perl as simple.
The Situation.
If the boss is advocating Perl, and Perl is not the answer, you will find it is very hard to convince someone they're wrong, making this effort nearly impossible.
If the boss was just throwing out ideas, then this is just difficult.
Quick Hack.
An easy thing you can do is to attempt head-to-head comparisons of Python and Perl for some randomly-chosen jobs. You can then have a code walkthrough to demonstrate the relative opacity of Perl compared with the relative clarity of Python.
Even this is fraught with terrible dangers.
Some folks really think code golf is important. Python loses at code golf. Perl wins. There's nothing worse than "Angry Co-worker with Perl Bias" who will kill you with code-golf solutions that -- because they're smaller -- can baffle management into thinking that they're clearer or "better" on some arbitrary scale.
Some folks really think explicit is "wordy" and bad. Python often loses because the assumptions are stated as actual parameter values. Some folks can (and do) complain at having to actually write things down. Read Stack Overflow for all of the Python questions where someone wants to make the try: block go away in a puff of assumptions.
If you choose random problems, you may -- accidentally -- chose something for which there's an existing piece of Perl or Python that can be downloaded and installed. A language can win just through an accident of the draw. Rather than a more in-depth comparison of language features.
Best Bet
The best you can do is the following.
Identify what folks value. You can call these "non-functional" requirements. These are quality factors. What are the foundational, core principles? Open, Accessible, Transferrable Skills, Simplicity, Cleanliness, Honesty, Integrity, Thriftiness, Reverence, Patience, Hard Work, A Sense of Perspective, Reef the Main in Winds over 20 kn, etc. This is hard. No sympathy here.
Identify the technical use cases. These are "functional" requirements. Which bits of glue and integration there are? This is hard, also. Requirements erupt of out of the woodwork when you do this. Also, when you have a Perl bigot on the team, numerous non-functional requirements will pile into this area. Your manager -- who proposed Perl -- may be the Perl bigot, and the use cases may be difficult to collect in the presence of a Perl bigot.
Identify how (a) Perl + Bash vs. (b) Python vs. (c) Java fit this core values and the functional requirements. Note that using Python means you do not need to use Bash as much. My preference, BTW, is to pare Bash down to the rock-bottom minimum.
This is a big, difficult job. It's hard to short-cut. If you find that Perl is not the answer and the Perl bigot you need to convince is the manager who proposed Perl in the first place, you may find that convincing someone that they're wrong is very hard.
Edit. I am aware that I am forbidden from using the string "Perl Bigot" to describe the manager's potential level of bias toward Perl. I, however, insist on using "Perl Bigot" to describe the manager who proposed Perl. The question provides no information on which to change this. The worst case is that (a) the manager is the Perl Bigot and (b) Perl is not the answer.

Jython or JRuby?

It's a high level conceptual question. I have two separate code bases that serve the same purpose, one built in Python and the other in Ruby. I need to develop something that will run on JVM. So I have two choices: convert the Python code to Jython or convert the Ruby to JRuby. Since I don't know any of them, I was wondering if anyone can give me some guidance. Like which one runs faster, or more importantly which one has tools available for easy code migration(.pyc to .jar files)?

In both cases, most of the code should Just Work™. I don't know of a really compelling reason to choose Jython over JRuby or vice versa if you'll be learning either from scratch. Python places a heavy emphasis on readability and not using "magic", but Ruby tends to give you a little more rope to do fancy things, e.g., define your own DSL. The main difference is in the community, and largely revolves around the different focus mentioned above.

If you are going to be investing time and effort into either platform you should check how active the development is on both platforms. Subscribe to the mailing lists and newsgroups to get an idea of the community, check the source control system for both projects and get a feeling for how active the development is.
I am more familiar with Python than Ruby. The Jython project after a period slow movement has really picked up momentum, a Python 2.5 compatible version was released in June. This is a major step forward as Python 2.5 introduces some very useful language enhancements: http://docs.python.org/whatsnew/2.5.html

The compatibility in either case is at the source-code level; with necessary changes where the Python or Ruby code invokes packages that involve native code (especially, standard Python packages like ctypes are not present in Jython).

Performance may be the deciding factor: in this benchmark (which, like all benchmarks, should be taken with a grain of salt), JRuby ran somewaht faster than native Ruby, while Jython was outperformed by CPython by a factor of 3.

Anything you can do in one, you can do in the other.
Learn enough of both to realise which one appeals to your coding sensibilities. There is no right or wrong answer here.

With Lua and Python embeddable, is there a place for Basic?

I started off programming in Basic on the ZX81, then BASICA, GW-BASIC, and QBasic. I moved on to C (Ah, Turbo C 3.1, I hardly knew ye...)
When I got started in microcontrollers I regressed with the BASIC Stamp from Parallax. However, BASIC is/was awesome because it was so easy to understand and so hard to make a mistake. I moved on to assembly and C eventually because I needed the additional power (speed, capacity, resources, etc.), but I know that if the bar was much higher many people would never get into programming microcontrollers.
I keep getting an itch to make my own on-chip BASIC interpretor, but I wonder if there's need for BASIC now that Lua and Python are easily embeddable, and just as approachable as BASIC.
What, if any, are the advantages BASIC has over other languages?
Why is it still around?
If I decide to make a general purpose microcontroller board with an interpreter, is there any reason to make a version of BASIC?
Plenty of other languages are considered dead, but BASIC just keeps hanging on.

[This may come off sounding more negative than it really is. I'm not saying Basic is the root of all evil, others have said that. I'm saying it's a legacy we can afford to leave behind.]
"because it was so easy to understand and so hard to make a mistake" That's certainly debatable. I've had some bad experiences with utterly opaque basic. Professional stuff -- commercial products -- perfectly awful code. Had to give up and decline the work.
"What, if any, are the advantages Basic has over other languages?" None, really.
"Why is it still around?" Two reasons: (1) Microsoft, (2) all the IT departments that started doing VB and now have millions of lines of VB legacy code.
"Plenty of other languages are considered dead..." Yep. Basic is there along side COBOL, PL/I and RPG as legacies that sometimes have more cost than value. But because of the "if it ain't broke don't fix it" policy of big IT, there they sit, sucking up resources who could easily replace it with something smaller, simpler and cheaper to maintain. Except it hasn't "failed" -- it's just disproportionately expensive.
30-year old COBOL is a horrible situation to rework. Starting in 2016 we'll be looking at 30-year old MS Basic that we just can't figure out, don't want to live without, and can't decide how to replace.
"but basic just keeps hanging on" It appears that some folks love Basic. Others see it as yet another poorly-designed language; it's advantages are being early to market and being backed by huge vendors (IBM, initially). Poorly-design, early-to-market only leaves us with a legacy that we'll be suffering with for decades.
I still have my 1965-edition Dartmouth Basic manual. I don't long for the good old days.

As an architecture, the main claim to fame of BASIC is that you could make BASIC interpreters very small - just a few KB. In the days of a DG Nova this was a win as you could use systems like Business BASIC to build a multiuser application on a machine with 64K of RAM (or even less).
BASIC (VB in particular) is a legacy system and has a large existing code-base. Arguably VB is really a language (some would say a thin wrapper over COM) that has a BASIC-like syntax. These days, I see little reason to keep the language around apart from people's familiarity with it and to maintain the existing code base. I certainly would not advocate new development in it (note that VB.Net is not really BASIC but just has a VB-like syntax. The type system is not broken in the way that VB's was.)
What is missing from the computing world is a relevant language that is easy to learn and tinker with and has mind-share in mainstream application development. I grew up in the days of 8-bit machines, and the entry barrier to programming on those systems was very low. The architecture of the machines was very simple, and you could learn to program and write more-or-less relevant applications on these machines very easily.
Modern architectures are much more complex and have a bigger hump to learn. You can see people pontificating on how kids can't learn to program as easily as they could back in the days of BASIC and 8-bit computers and I think that argument has some merit. There is something of a hole left that makes programming just that bit harder to get into. Toy languages are not much use here - for programming to be attractive it has to be possible to aspire to build something relevant with the language you are learning.
This leads to the problem of a language that is easy for kids to learn but still allows them to write relevant programmes (or even games) that they might actually want. It also has to be widely perceived as relevant.
The closest thing I can think of to this is Python. It's not the only example of a language of that type, but it is the one with the most mind-share - and (IMO) a perception of relevance is necessary to play in this niche. It's also one of the easiest languages to learn that I've experienced (of the 30 or so that I've used over the years).

Why not give Jumentum a try and see how it works for you?
http://jumentum.sourceforge.net/
it's an open source BASIC for micrcontrollers
The elua project is also lua for microcontrollers
http://elua.berlios.de/

BASIC persists, particularly in the STAMP implementation, because it is lower level than most other very-easy-to-learn programming languages. For most embedded BASIC implementations the BASIC instructions map directly to single or groups of machine instructions, with very little overhead. The same programs written in "higher level" languages like Lua or Python would run far slower on those same microcontrollers.
PS: BASIC variants like PBASIC have very little in common with, say, Visual BASIC, despite the naming similarity. They have diverged in very different ways.

Good question...
Basically (sic!), I have no answer. I would say just that Lua is very easy to learn, probably as easy as Basic (which was one of my first languages as well, I used dialects on lot of 8-bit computers...), but is more powerful (allowing OO or functional styles and even mixing them) and somehow stricter (no goto...).
I don't know well Python, but from what I have read, it is as easy, powerful and strict than Lua.
Beside, both are "standardized" de facto, ie. there are no dialects (beside the various versions), unlike Basic which has many variants.
Also both have carefully crafted VM, efficient, (mostly) bugless. Should you make your own interpretor, you should either take an existing VM and generate bytecode for it from Basic source, or make your own. Sure fun stuff, but time consuming and prone to bugs...
So, I would just let Basic have a nice retirement... :-P
PS.: Why it is hanging on? Perhaps Microsoft isn't foreign to that... (VB, VBA, VBScript...)
There are also lot of dialects around (RealBasic, DarkBasic, etc.), with some audience.

At the risk of sounding like two old-timers on rocking chairs, let me grumpily say that "Kids today don't appreciate BASIC" and then paradoxically say "They don't know how good they've got it."
BASICs greatest strength was always its comprehensibility. It was something that people could get. That was long ignored by academics and language developers.
When you talk about wanting to implement BASIC, I assume you're not talking about line-numbered BASIC, but a structured form. The problem with that is that as soon as you start moving into structured programming -- functions, 'why can't I just GOTO that spot?', etc. -- it really becomes unclear what advantages, if any, BASIC would have over, say, Python.
Additionally, one reason BASIC was "so easy to get right" was that in those days libraries weren't nearly as important as they are today. Libraries imply structured if not object-oriented programming, so again you're in a situation where a more modern dynamic scripting language "fits" the reality of what people do today better.
If the real question is "well, I want to implement an interpreter and so it comes down to return on investment," then it becomes a problem of an grammar that's actually easy to implement. I'd suggest that BASIC doesn't really have that many advantages in that regard either (unless you really do return to line numbers and a very limited grammar).
In short, I don't think you should invest your effort in a BASIC interpreter.

Well, these people seem to think that not only basic still has a place in the mobile space but also that they can make money off it:
http://www.nsbasic.com/symbian/

I started out on a ZX81 too. But as Tony Hoare said, programming in BASIC is like trying to do long division using roman numerals.
Plenty of other languages are
considered dead, but basic just keeps
hanging on.
Sadly yes. I blame Bill Gates for this...BASIC was on a stretcher with a priest saying the last rites for it, and then MS brought it back like Smallpox.

I used to program in BASIC in the QBasic days. QBASIC had subroutines, functions, structures (they used to be called types), and I guess that's it. Now, this seems limited compared to all the features that Python has - OO, lambdas, metaclasses, generators, list comprehensions, just to name a few off the top of my head. But that simplicity, I think, is a strength of BASIC. If you're looking at a simple embeddable language, I'd bet that QBasic will be faster and easier to understand. And a procedural langauge is probably more than sufficient for most embedding/scripting type of applications.
I'd say the most important reason BASIC is still around is Visual Basic. For a long time in the 90s, VB was the only way to write GUIs, COM and DB code for Windows without falling into one of the C++ Turing tarpits. [Maybe Delphi was a good option too, but unfortunately it never became as popular as VB]. I do think it is because of all this VB and VBA code that is still being used and maintained that BASIC still isn't dead.
That said, I'd say there's pretty a good rationale to write BASIC interpreter (maybe even compiler using LLVM or something similar) for BASIC today. You'll get a clean, simple easy to use and fast language if you implement something that resembles QBasic. You won't have to solve any language design issues and the best part is people will already know your language.