Let me say first that I'm NOT searching for automagical solutions here. I want to translate code from Python to Smalltalk because I've noticed some very simple sentences can be automatically translated, examples:
Assigning a variable to a value
Python
i = 1
Smalltalk
i := 1.
Creating a new instance of a class
Python
instance = module.ClassName()
Smalltalk
instance := ClassName new.
A for loop
Python
for a in [0,1,2]:
print (str(a)+str(a))
Smalltalk
#(0 1 2) do: [: a | Transcript show: a + a; cr ]
and so on (while loops, conditionals, etc). My idea is to have a tool which translates all this extremely "simple" cases, and then I may complete or teach a rule system by hand.
Do you know any programming translation tool or library which can help me?
In case you haven't heard of any tool, what technique/pattern you will use to implement such translation? Can you provide a link to an example?
Thanks
You need to parse the Python code, walk the abstract syntax tree that is generated by the parser and output your Smalltalk. There's a nice article about Python ASTs by Eli Bendersky and a slightly older one here. Python makes this relatively straight forward as the Python standard library exposes a lot of the internal tooling of the interpreter and the documentation is reasonably comprehensive.
I am not aware of any such tool, and in general case it might be complicated and/or inefficient. So your route would depend on your more precise need: porting an existing python library, just using it from smalltalk, or making nice clean smalltalk code that does the same thing as python one.
Routes I would consider:
leaving python library as is, and calling it from smalltalk through c interface
implementing python parser in pettit parser an then:
implement smalltalk generator maybe assisted by human through user interface
python interpreter in smalltalk
Note that generator variant might face some difficult issues in general cases, for instance smalltalk has fixed number of instance variables, while in python you can attach then as you go. You could work around that, but resulting smalltalk code might not be pretty.
As for implementing python inside smalltalk take a look at the helvetia presentation from Lukas Renggli, it is on the subject of including other languages inside smalltalk IDE.
Take a look at ply, which is a Lex-Yacc Python implementation. I've used it mostly for translating some other language into Python byte code by building a Python AST with it, but the opposite should be also possible.
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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...
I recall when I first read Pragmatic Programmer that they suggested using scripting languages to make you a more productive programmer.
I am in a quandary putting this into practice.
I want to know specific ways that using Python or Ruby can make me a more productive .NET developer.
One specific way per answer, and even better if you can say whether I could use Python or Ruby or Both for it.
See standard format below.
IronPython / IronRuby
IronPython in Action will do a better job explaining this (and exactly how best to use IronPython) that can possibly be accommodated in a SO answer. I'm biased -- I was a tech reviewer and am a friend of one of the authors -- but objectively think it's a great book. (No idea if IronRuby is blessed with a similarly wonderful book, yet).
As you want "one specific way per answer" (incompatible with SO, which STRONGLY discourages a poster posting 25 different answers if they have 25 "specific ways" to indicate...!-): prototyping in order to explore some specific assembly or collection thereof that you're unfamiliar with (to check if you've understood their docs right and how to perform certain tasks) is an order of magnitude more productive in IronPython than in C#, as you can explore interactively and compilation is instantaneous and as-needed. (Have not tried IronRuby but I'll assume it can work in a roughly equivalent way and speed).
Less Code
I think productivity is direct result on how proficient you are in a specific language. That said the terseness of a language like Python might save some time on getting certain things done.
If I compare how much less code I have to write for simple administration scripts (e.g. clean-up of old files) compared to .NET code there is certain amount of productivity gain. (Plus it is more fun which also helps getting the job done)
Advanced Text Processing
Traditional strengths of awk and perl. You can just glue together a bunch of regular expressions to create a simple data-mining system on the go.
Learning a new language gives you knowledge that you can bring back to any programming language. Here are some things you'd learn.
Add functionality to your objects on the fly.
Mix in modules.
Pass a chunk of code around.
Figure out how to do more with less code: ruby -e "puts 'hello world'"
C# can do some of these things, but a fresh perspective might bring you one step closer to automating your breakfast.
Embedding a script engine
Use of IronPython for a scripting engine inside your .NET application. For example enabling end-users of your application to change customizable parts with a full fledge language such as Python.
A possible example might be to expose custom logic to end-users for a work flow engine.
Quick Prototyping - Both
In the simplest cases when firing a python interpreter and writing a line or two is way faster than creating a new project in visual studio.
And you can use ruby to. Or lua, or evel perl, whatever. The point is implicit typing and light-weight feel.
Cross platform
Compared to .NET a simple script Python is more easily ported to other platforms such as Linux. Although possible to achieve the same with the likes of Mono it simpler to run a Python script file on different platforms.
Processing received Email
Python has built-in support for POP3 and IMAP where the standard .NET framework doesn't. Useful for automating email triggered tasks.
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.
I'm currently reading a great book called 'Programming Collective Intelligence' by Toby Segaran (which i highly recommend)
The code examples are all written in Python, and as I have already learnt one new language this year (graduating from VB.net to C#) i'm not keen to jump on another learning curve.
This leaves my with the issue of translating the python examples into C#.
Question is: How critical is it that the code stay in python? Are there thing in python that I can't do in a normal managed statically typed language?
One challenge you'll find is that not only are the algorithms implemented in Python, but the book makes extensive use of Python libraries like BeautifulSoup, Numpy, PIL, and others (see appendix A).
I doubt there are any specifics of the algorithms that you couldn't port to another language, but you'll have trouble working through the exercises. Also, to translate the code, you'll have to learn Python at least a little bit, no?
I suggest you just dive in and learn Python. You can use IronPython if you have any concern about interoperability with your C# projects.
You can do the same things in all Turing-complete languages. Here is an example for rendering a Mandelbrot fractal in SQL. The example shows: Even if you can use any language, the effort will be different.
So my guess is that the code will become much longer since Python is so flexible and open.
I suggest translating them to C#. I have been porting chapter 2 "Recommendations" to VB.Net. Along the way I'm learning Python as a side-effect. Toby does some amazing things with Python lists.
Dealing with the the extra Python libraries is another story. Ndelicious is a close match to pyDelicious, but it is missing a few key features (popular posts!).
Obligatory XKCD: http://xkcd.com/353/
I know you explicitly say you don't want to learn Python (this year), but translating the Python examples to C# will definitely be a much steeper curve. Just dive in!
The book is about algorithms, not the details of programming, and the language of choice is just to make the examples concrete. As the author says, "The code examples in this book are written in Python... but I provide explanations of all the algorithms so that programmers of other languages can follow." (p. xv)
Python is a great language and easy to learn, but I suspect the difficulties in applying ideas from the book will not be in the translating of the code to another language or set of libraries, but in understanding the ideas and modifying the code to suite your needs. I think there are two main reasons to stay with a language you're familiar with: 1) when your code doesn't work, if you're writing in an unfamiliar language, you won't know where to start looking for errors, e.g. if you're like most people you'll even start wondering if it's due to a bug in Python, which it won't be, but you'll wonder and it will distract. 2) There are just natural limits to how much you can remember in a certain length of time; and learning a language at the same time will give you twice as much to remember.
It depends though how well you know C#, and what you lose by leaving it.
Python seems to be to AI programming what LISP was for for many decades. Russel/Norvig's famous book AI: A Modern Approach also provides lots of examples in Python.