Interpreter in Python: Making your own programming language? - python

Remember, this is using python.
Well, I was fiddling around with an app I made called Pyline, today. It is a command line-like interface, with some cool features. However, I had an idea while making it: Since its like a "OS", wont it have its own language?
Well, I have seen some articles online on how to make a interpreter, and parser, and compiler, but it wasn't really readable for me. All I saw was a crapload of code. I am one of those guys who need comments or a readme or SOME form or communication towards the user without the code itself, so I think that Stack Overflow would be great for a teenager like me. Can I get some help?

You need some grounding first in order to actually create a programming language.
I strongly suggest picking up a copy of Programming Language Pragmatics, which is quite readable (much more so than the Dragon book) and suitable for self study.
Once you are ready to start messing with parsers, ANTLR is the "gold" standard for parser generators in terms of usability (though flex+bison/yacc are quite capable).

I just came by Xtext, a language development framework. Perhaps that's something you might want to take a look at.
Considering Python you might find it instructive to implement a version of Logo. If you want, you can skip the parsing/lexing stage for now and come up with a object oriented version first to get you going if your OOP skills are up to it. Later on you can hook it up with some graphics library to actually draw something.
In addition to Logo you might want to check out L-systems. See particularly The Algorithmic Beauty of Plants for inspiration.

Like theatrus, I'd suggest starting with a good book on the subject. I can definitely recommend Language Implementation Patterns by Terence Parr (the man behind ANTLR, a common parser generator).

See Peter Norvig's Scheme interpreter in 2 pages of Python with plenty of explanation. There's also a fancier version linked from there, worth reading once you've grokked the simpler one.

Related

Python for a hobbyist programmer ( a few questions)

I'm a hobbyist programmer (only in TI-Basic before now), and after much, much, much debating with myself, I've decided to learn Python. I don't have a ton of free time to teach myself a hundred languages and all programming I do will be for personal use or for distributing to people who need them, so I decided that I needed one good, strong language to be good at. My questions:
Is python powerful enough to handle most things that a typical programmer might do in his off-time? I have in mind things like complex stat generators based on user input for tabletop games, making small games, automate install processes, and build interactive websites, but probably a hundred things along those lines
Does python handle networking tasks fairly well?
Can python source be obfuscated, or is it going to be open-source by nature? The reason I ask this is because if I make something cool and distribute it, I don't want some idiot script kiddie to edit his own name in and say he wrote it
And how popular is python, compared to other languages. Ideally, my language would be good and useful with help found online without extreme difficulty, but not so common that every idiot with computer knows python. I like the idea of knowing a slightly obscure language.
Thanks a ton for any help you can provide.
Is python powerful enough to handle
most things?
Yes. Period. Study EveOnline game for more information. Look at pygame framework. Free free to use Google to find more.
Does python handle networking tasks
fairly well?
Yes. Look at the number of Python web frameworks plus the Twisted framework. Feel free to use Google to search for Python networking.
Can python source be obfuscated?
Not usefully. This isn't C.
And how popular is python, compared to
other languages?
Look at the TIOBE index.
I think that Python is very powerful to do a lot of things, but just like Java and C++, it often depends on good third-party libraries. I come from a Java background but use Python for a lot of things, and it's been a fun ride. I've done things like statistics, and automation, not sure about the UI though that often depends on the toolkit more than the language.
Python networking works well. I don't know if I'd use it to build a fast algorithmic trading system or a VOIP application, but for most intents and purposes, especially at higher levels of abstraction, it's fine and easy to use. You would need external libraries for things like SSH or FTP.
Python is quite popular and has very good online support, active community, and major corporations (likeGoogle) that use it. I found the official online tutorial and reference to be excellent.
I have to say that I disagree with the "every idiot with a computer" line. There's a difference between knowing a language and using it right, and that's true about every language, even natural ones :) Python does have a lot of functional elements that are not as trivial to use for people coming from a procedural background, so there's always room for growth.
The one problem with Python compared to languages like C and Java is that it is not statically typed. This makes it much faster to write code, but also makes it *much easier) to make mistakes that can be quite nasty to debug. For instance, the same variable can contain a String reference at some point, and a reference to a list of strings at some other point.
Absolutely.
What type of networking? It has socket, http, xml, smtp/pop, telnet, and much more built in.
Python obfuscation won't be nearly as good as a compiled language. Usually that isn't a problem.
It's the 9th most popular tag on stackoverflow, so there's plenty of help available.
Is python powerful enough to handle most things that a typical programmer might do in his off-time? I have in mind things like complex stat generators based on user input for tabletop games, making small games, automate install processes, and build interactive websites, but probably a hundred things along those lines
Definitely. Python is a good tool for all of those except automating install processes, where it might be the right tool but more likely the right tool will likely be decided by what specifically you are automating.
Does python handle networking tasks fairly well?
Yes. You will want to look into Twisted.
Can python source be obfuscated, or is it going to be open-source by nature? The reason I ask this is because if I make something cool and distribute it, I don't want some idiot script kiddie to edit his own name in and say he wrote it
"Open source" refers to the licensing of your code, not the viewability of its source code. Hiding Python source code isn't especially possible, and the results of decompiling Python bytecode will result in much more readable code than the equivalent tools in languages like C. Don't worry about this! You can't prevent people from stealing your car or your computer if they are willing to break the law, and you can't do the same for your code in any language.
And how popular is python, compared to other languages. Ideally, my language would be good and useful with help found online without extreme difficulty, but not so common that every idiot with computer knows python. I like the idea of knowing a slightly obscure language.
This is an unanswerable question. Google will give you lots of conflicting results with different metrics, most of them useful. You're also being a bit silly ;)
As far as learning materials go, I recommend How to Think Like a Computer Scientist, which is a good text that does not presume any existing programming knowledge. It is available for free online, or you could buy a print copy if you prefer. (Don't bother learning 3.x yet. There is not enough library support to do much useful stuff like you want to do, and when there is picking it up will be a breeze; it's not very different than 2.5/6/7.)
Probably yes. Maybe the stat crunching thing will be kinda slow, and maybe a game depending on what kind of game, but generally the performance is good enough, and you save a lot of time on the actual programming. If you REALLY need performance, you can make a module in C, but usually there is a library written to do what you want..
I haven't used it, but there's a framework called Twisted that seems to be pretty good.
No. Bytecode can be decompiled easily, and it only works on a specific version of Python, so your code isn't as portable.
Python is pretty popular, and the Python Package Index has a big list of third party libraries. It's not as widespread as, say, Java, but a lot of people use it and you can probably get answers for what you want.
Points 1 and 2: HELL YEAH.
Point 4: kind of. Python is good at some network stuff. It's not Java or C++. Just use zlib (zip library) and pickle (serialization) for everything, and look at xmlrpclib if you need IPC.
Point 3: No. However, you can write C modules (for the performance critical, and hard-to-copy) parts of your code, and that would make it non-trivial to reverse-engineer.
Python is up to the task (and better) for 1, 2 and 4.
The best solution for 3 from what you describe would probably be to make your programs really open-source with GPL or BSD like licence. This way people will edit your super-cool sources (but often experienced programmers, not just script kiddies) and build on then but leave your name in for posterity.

Python programming general questions

I heard that Python is easy and powerful, but I don't know if I'm on the right track to learn it. I learn from online tutorials, I know basic maths calculation and printing strings, but how long will it take to develop something useful? I don't really know the exact uses of Python, though.
I'm not exactly sure what you're looking for, but I think one or more of the following may be the next step you're looking for.
Perhaps you would like to use a variety of different protocols for a networking program, you could check out Twisted.
Or perhaps if you would like to make a web application or blog you can check out Django.
Or perhaps you would like to make a GUI application, you could take a look at TkInter.
Or perhaps you would like to get into game programming, you could take a look at Pygame.
Or perhaps you would like to ... you can take a look at the Python Package Index.
How long will it take? This depends on your programming background in general. The best way is simply to jump into the topic you're interested in and start on a mini project.
Python is a general purpose language. You can use it to make a lot of different things, but it's best suited at stuff that doesn't require a lot of speed, since the high level features have a performance cost.
It's hard to tell how long it will take you to develop something useful. The other day I made a script to help on a small computer administration thing. You could do that with a week or two of experience (or maybe less), depending on your previous programming knowledge and the amount of time you put into studying. However, if you want to make something bigger (maybe an audio player, an IM client, mid-sized stuff like that), you probably need some weeks or months of practice. It depends a lot on the time and energy you invest in programming.
I'd suggest to follow either the official tutorial or Dive Into Python.
In general, it depends on you. Python can be used for simple or complex stuff, and for many different applications. It depends on what you want.
Have a look at Mark Pilgrim's freely available book called Dive Into Python. I think it's a better choice to start with than online tutorials. The best way to learn a language is to start to work on a project. As I read this book, I started to implement a simple image viewer. As I advanced with the book, I could refine the project progressively. Invent something that is interesting to you.
I also suggest you taking notes when you learn a programming language. When you learn something that can be useful later, make some notes with a simple example, e.g. how to read a text file line by line, convert int to str, convert str to int, basic list operations, etc. Later on you can use these building blocks in a larger project.
Like every other programming language In order to learn Python you need to write a program with it.
Find a pet project and use python to code it. I also recommend Dive into python" (like anyone else that answered your question).
A few months ago I've decided to learn IronPython (.NET implementation of python), I'vve started by reading "Dive into python" and a few tutorials and then I've started coding a simple board game using IronPython (you can read about it in my blog).
In order to learn a new programming language you need to use it and then you'll know how and where to use it.
The best way to learn how to do something useful is come up with something useful you want to do. Make sure it's not way out of your league, then do research to accomplish it. That's how a lot of programmers learn languages.
What other programming background do you have? What programming interests do you have -- web apps, numerical / scientific computations, games, ...? Python is good at many different things, for both beginners and experienced programmers, but the most fruitful approach(es) to it do depend on what you already know, and what really interests you!-)
Bram who invented bittorrent with python says python is good for writing protocols in addition to aforementioned webapps, games and general purpose. Compared to Java python solves same problem in less code and less ways in longer development and VM time where Java has more ways solve same problem in more code and faster VM and faster development time.
Making a comparison between Python, and other languages would not help, as there is always somebody who would find a reason to prefer one language instead of another.
If you want a scripting language that is powerful, but that it is easier to read than perl, that doesn't have a curly bracket syntax, and that allows you to learn something about object oriented programming, then Python is the language for you.

Next step after PHP: Perl or Python? [closed]

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It might seem it has been asked numerous times, but in fact it hasn't. I did my research, and now I'm eager to hear others' opinions.
I have experience with PHP 5, both with functional and object oriented programming methods. I created a few feature-minimalistic websites.
Professionals may agree about PHP not being a programming language that encourages good development habits. (I believe it's not the task of the tool, but this doesn't matter.) Furthermore, its performance is also controversial and often said to be poor compared to competitors.
In the 42nd podcast at Stack Overflow blog a developer from Poland asked what language he should learn in order to improve his skills. Jeff and Joel suggested that every one of them would help, altough there are specific ones that are better in some ways.
Despite they made some great points, it didn't help me that much.
From a beginner point of view, there are not one may not see (correction suggested by S. Lott) many differences between Perl & Python. I would like You to emphasize their strenghts and weaknesses and name a few unique services.
Of course, this wouldn't be fair as I could also check both of them. So here's my wishlist and requirements to help You help me.
First of all, I'd like to follow OOP structures and use it fundamentally. I partly planned a multiuser CMS using MySQL and XML, so the greater the implementations are, the better. Due to its foreseen nature, string manipulation will be used intensively.
If there aren't great differences, comparisons should probably mention syntax and other tiny details that don't matter in the first place.
So, here's my question: which one should I try first -- Perl || Python?
Conclusion
Both Perl and Python have their own fans, which is great. I'd like to say I'm grateful for all participation -- there is no trace of any flame war.
I accepted the most valued answer, although there are many great mini-articles below. As suggested more often, I will go with Python first. Then I'll try Perl later on. Let me see which one fits my mind better.
During the development of my special CMS, I'm going to ask more regarding programming doubts -- because developers now can count on each other! Thank you.
Edit: There were some people suggesting to choose Ruby or Java instead. Java has actually disappointed me. Maybe it has great features, maybe it hasn't. I wouldn't enjoy using it.
In addition, I was told to use Ruby. So far, most of the developers I communicate with have quite bad opinion about Ruby. I'll see it myself, but that's the last element on my priority list.
Perl is a very nice language and CPAN has a ton of mature modules that will save you a lot of time. Furthermore, Perl is really moving forwards nowadays with a lot of interesting projects (unlike what uninformed fanboys like to spread around). Even a Perl 6 implementation is by now releasing working Perl 6.
I you want to do OO, I would recommend Moose.
Honestly, the "majority" of my programming has been in Perl and PHP and I recently decided to do my latest project in Python, and I must admit it is very nice to program with. I was hesitant of the whole no curly braces thing as that's what I've always done, but it is really very clean. At the end of the day, though, you can make good web applications with all 3, but if you are dead-set on dropping PHP to try something new I would recommend Python and the Django framework.
I'd go with Perl. Not everyone will agree with me here, but it's a great language well suited to system administration work, and it'll expose you to some more functional programming constructs. It's a great language for learning how to use the smallest amount of code for a given task, as well.
For the usage scenario you mentioned though, I think PHP may be your best bet still. Python does have some great web frameworks, however, so if you just want to try out a new language for developing web applications, Python might be your bet.
I have no experience with Python. I vouch strongly to learn Perl, not out of attrition, but because there is a TON to learn in the platform. The key concepts of Perl are: Do What I Mean (DWIM) and There's More Than One Way To Do It (TMTOWTDI). This means, hypothetically there's often no wrong way to approach a problem if the problem is adequately solved.
Start with learning the base language of Perl, then extend yourself to learning the key Perl modules, like IO::File, DBI, HTML::Template, XML::LibXML, etc. etc. search.cpan.org will be your resource. perlmonks.org will be your guide. Just about everything useful to do will likely have a module published.
Keep in mind that Perl is a dynamic and loosely structured language. Perl is not the platform to enforce draconian OOP standards, but for good reason. You'll find the language extremely flexible.
Where is Perl used? System Admins use it heavily, as already mentioned. You can still do excellent web apps either by simple CGI or MVC framework.
I haven't worked with Python much, but I can tell why I didn't like about Perl when I used it.
OO support feels tacked on. OO in perl is very different from OO support in the other languages I've used (which include things like PHP, Java, and C#)
TMTOWTDI (There's More Than One Way To Do It). Good idea in theory, terrible idea in practice as it reduces code readability.
Perl uses a lot of magic symbols.
Perl doesn't support named function arguments, meaning that you need to dig into the #_ array to get the arguments passed to a function (or rather, a sub as perl doesn't have the function keyword). This means you'll see a lot of things like the example below (moved 'cause SO doesn't like code in numbered lists)
Having said all that, I'd look into Python. Unless you want to go with something heavier-weight like C++ or C#/Java.
Oh, before I forgot: I wanted to put an example for 4 above, but SO doesn't like putting code in numbered lists:
sub mySub {
#extremely common to see in Perl, as built-ins operators operate on the $_ scalar or #_ array implicitly
my $arg1 = shift;
my $arg2 = shift;
}
I recently made the step from Perl over to Python, after a couple of Perl-only years. Soon thereafter I discovered I had started to read through all kinds of Python-code just as it were any other easy to read text — something I've never done with Perl. Having to delve into third-party Perl code has always been kind of a nightmare for me, so this came as a very very nice surprise!
For me, this means Python-code is much easier to maintain, which on the long run makes Python much more attractive than Perl.
Python is clean and elegant, and the fact that LOTS of C APIs have been wrapped, gives you powerful hooks to much. I also like the "Zen of Python".
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to
do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than right now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
As a Perl programmer, I would normally say Perl. But coming from PHP, I think Perl is too similar and you won't actually get that much out of it. (Not because there isn't a lot to learn, but you are likely to program in Perl using the same style as you program in PHP.)
I'd suggest something completely different: Haskell (suggested by Joel), Lisp, Lua, JavaScript or C. Any one of these would make you a better programmer by opening up new ways of looking at the world.
But there's no reason to stop learning PHP in the meantime.
For a good look at the dark side of these languages, I heartily recommend: What are five things you hate about your favorite language?
I suggest going through a beginner tutorial of each and decide for yourself which fits you better. You'll find you can do what you need to do in either:
Python Tutorial (Python Classes)
Perl Tutorial (Perl Classes)
(Couldn't find a single 'official' perl tutorial, feel free to suggest one)
In my experience python provides a cleaner, more straight-forward experience.
My issues with perl:
'use strict;', Taint, Warnings? - Ideally these shouldn't be needed.
Passing variables: #; vs. $, vs shift
Scoping my, local, ours? (The local defintion seems to particularly point out some confusion with perl, "You really probably want to be using my instead, because local isn't what most people think of as "local".".)
In general with my perl skills I still find my self referencing documentation for built-in features. Where as in python I find this less so. (I've worked in both roughly the same amount of time, but my general programming expereince has grown with time. In other words, I'd probably be a better perl programmer now)
If your a unix command line guru though, perl may come more naturally to you. Or, if your using it mainly as a replacement or extension to command line admin tasks, it may suit your needs fine. In my opinion perl is "faster on the draw" at the command line than python is.
Why isn't there Ruby on your list? Maybe you should give it a try.
"I'd like to follow OOP structure..." advocates for Python or, even more so if you're open, Ruby. On the other hand, in terms of existing libraries, the order is probably Perl > Python >> Ruby. In terms of your career, Perl on your resume is unlikely to make you stand out, while Python and Ruby may catch the eye of a hiring manager.
As a PHP programmer, you are probably going to see all 3 as somewhat "burdensome" to get a Web page up. All have good solutions for Web frameworks, but none is quite as focussed on rendering a Web page as is PHP.
I think that Python is quite likely to be a better choice for you than Perl. It has many good resources, a large community (although not as large as Perl, probably), "stands out" a little on a resume, and has a good reputation.
If those 2 are your only choices, I would choose Python.
Otherwise you should learn javascript.
No I mean really learn it...
If you won't be doing web development with this language, either of them would do. If you are, you may find that doing web development in perl is a bit more complicated, since all of the frameworks require more knowledge of the language.
You can do nice things in both, but my opinion is that perl allows more rapid development. Also, perl's regexes rock!
Every dynamic language is from same family. It does not matter Which is the tool you work with it matter how you do..
PHP VS PYTHON OT PERL OR RUBY? Stop it
As many comments mentioned python is cleaner well sometime whose curly brackets are use full to. You just have to practice.

Please advise on Ruby vs Python, for someone who likes LISP a lot

I am a C++ developer, slowly getting into web development. I like LISP a lot but don't like AllegroCL and web-frameworks available for LISP. I am looking for more freedom and ability to do cool hacks on language level. I don't consider tabs as a crime against nature.
Which one is closer to LISP: Python or Ruby?
I can't seem to be able to choose from Python and Ruby: they seem very similar but apparently Ruby is more functional and object-oriented, which are good things, while Python is more like Perl: a simple scripting language. Do I have the right impression?
PS - This might seem like a flame bait but it's not really, I'm just trying not to go crazy from OCD about switching from RoR to Python/Django and back.
Peter Norvig, a famous and great lisper, converted to Python. He wrote the article Python for Lisp Programmers, which you might find interesting with its detailed comparison of features.
Python looks like executable pseudo-code. It's easy to pick up, and often using your intuition will just work. Python allows you to easily put your ideas into code.
Now, for web development, Python might seem like a more scattered option than Ruby, with the plethora of Python web frameworks available. Still, in general, Python is a very nice and useful language to know. As Ruby and Python's niches overlap, I agree with Kiv that it is partly a matter of personal taste which one you pick.
I'd go with Ruby. It's got all kinds of metaprogramming and duck punching hacks that make it really easy to extend. Features like blocks may not seem like much at first, but they make for some really clean syntax if you use them right. Open classes can be debugging hell if you screw them up, but if you're a responsible programmer, you can do things like 2.days.from_now (example from Rails) really easily (Python can do this too, I think, but with a bit more pain)
PS: Check out "Why Ruby is an acceptable LISP".
Devils Advocate: Who Cares?
They are both good systems and have an ecosystem of good web frameworks and active developer communities. I'm guessing that you're framing your decision based on the wrong criteria. The question sounds like you're fretting about whether you will hit implementation problems or other difficulties by choosing one over the other. Don't.
This is similar to Java/.Net decisions. There may be compelling reasons in a specific instance, but soft factors like the architect's familiarity with the platform are a much stronger predictor of project success.
I will admit that I've used Python much more than Ruby, but I wouldn't say that I have any great preference between the two apart from familiarity. I've used Python off and on since about 1998 and I like the Smalltalkish-ness of Ruby as I used Smalltalk briefly about 15 years ago. They both do similar things slightly differently.
I would like certain features from Ruby (or Smalltalk for that matter) but Python doesn't work that way. Instead, it has other features and language idioms are slightly different from Ruby or Smalltalk. Several of the other posters have linked out to articles that compare the two.
If you're worrying about Rails vs. Django, that suggests you're looking for a platform for web applications. Both languages have good tool support and an active developer community. Django seems to be the winner of the Python web framework melee and Rails seems to be in the process of 'crossing the chasm' and bringing Ruby along with it. Both are reasonably mature systems and have been demonstrated to work well for respectable traffic volumes.
ProTip: The presence of religious wars is a good indicator that neither side has a compelling arguement.
So, I'm going to play devil's advocate and say that worrying about the choice is pointless. The languages have advantages and disadvantages with respect to each other but nothing that could be viewed as compelling in the general case. Fretting about the detailed merits of one platform or the other is framing the decision wrongly.
Pick one and use it. You will be able to build systems effectively with either.
Speaking as a "Rubyist", I'd agree with Kiv. The two languages both grant a nice amount of leeway when it comes to programming paradigms, but are also have benefits/shortcomings. I think that the compromises you make either way are a lot about your own programming style and taste.
Personally, I think Ruby can read more like pseudo-code than Python. First, Python has active whitespace, which while elegant in the eyes of many, doesn't tend to enter the equation when writing pseudo-code. Also, Ruby's syntax is quite flexible. That flexibility causes a lot of quirks that can confuse, but also allows code that's quite expressive and pretty to look at.
Finally, I'd really say that Ruby feels more Perl-ish to me. That's partly because I'm far more comfortable with it, so I can hack out scripts rather quickly. A lot of Ruby's syntax was borrowed from Perl though, and I haven't seen much Python code that feels similar (though again, I have little experience with Python).
Depending on the approach to web programming you'd like to take, I think that the types of web frameworks available in each language could perhaps be a factor in deciding as well. I'd say try them both. You can get a working knowledge of each of them in an afternoon, and while you won't be writing awesome Ruby or Python, you can probably establish a feel for each, and decide which you like more.
Update: I think your question should actually be two separate discussions: one with Ruby, one with Python. The comparisons are less important because you start debating the merits of the differences, as opposed to which language will work better for you. If you have questions about Ruby, I'd be more than happy to answer as best I can.
Both Ruby and Python are fairly distant from the Lisp traditions of immutable data, programs as data, and macros. But Ruby is very nearly a clone of Smalltalk (and I hope will grow more like Smalltalk as the Perlish cruft is deprecated), and Smalltalk, like Lisp, is a language that takes one idea to extremes. Based on your desire to do cool hacks on the language level I'd go with Ruby, as it inherits a lot of the metaprogramming mindset from Smalltalk, and that mindset is connected to the Lisp tradition.
Alex Martelli gives a good analysis of the subject. It's a bit dated now, but I agree with the basic gist of it: Python and Ruby are two different ways of implementing the same thing. Sure there are some things you can do in Ruby that you can't do in Python. And sure Python's syntax is (arguably) better than Ruby's. But when you get down to it, there's not a whole lot of objective, scientific reason to prefer one over the other.
A common thing that you will hear is this: the platform is more important than the language and Python has a better platform than Ruby (this argument works both ways so don't vote me down, all you rubyists). And there is some truth to it. Unfortunately, it's not very relevant though. If you dislike the platform for either languages, there are implementations of both in Java and .Net, so you can use those if you have concerns about the platform.
I also recommend the article by Peter Norvig that namin posted. If you want to look at functional programming in Python check out the functools module in the standard library.
There is also a lot of room to hack around in Python; private variables are by convention and not enforced, so you can poke around in the internal state of objects if you feel like it. Usually this is not necessary, though.
Both Ruby and Python are very object-oriented and support functional programming; I wouldn't say either one is clearly superior for your project; it's partly a matter of personal taste.
I am a Pythonista; however, based on your requirements, especially the "cool hacks on the language level", I would suggest you work on Ruby. Ruby is more flexible in the Perl way and you can do a lot of hacks; Python is targeted towards readability, which is a very good thing, and generally language hacks are a little frowned upon. Ruby's basic types can be modified in a hackish way that typically prototype languages allow, while Python's basic types are more suited for subclassing.
By the way, I would add a minor correction: both Ruby and Python are very, very object-oriented, and neither is intended to be used for quick-and-dirty scripts the Perl way. Among the two, Ruby is syntactically more similar to Perl than Python.
If you need Unicode support, remember to check how well supported it is. AFAIK, Python's support for Unicode is better than Ruby's, especially since Python 3.0. On the other hand, Python 3 is still missing some popular packages and 3rd party libraries, so that might play against.
I'm a Rubyist who chose the language based on very similar criteria. Python is a good language and I enjoy working with it too, but I think Ruby is somewhat more Lispy in the degree of freedom it gives to the programmer. Python seems to impose its opinions a little bit more (which can be a good thing, but isn't according to our criteria here).
Python certainly isn't more Perlish— Ruby is essentially a Smalltalk/Perl mashup (some of its less-used features are pulled directly from Perl), whereas Python is only distantly related to either.
pick the most popular one for your domain so your work gets the most visibility. some might say ruby/rails for web, python for everything else. picking a language just because its like lisp is really not appropriate for a professional.
If you like lisp, I think you'll be better like ruby but c++ reminds me more of python. I've posted a small post about this subject : http://hartator.wordpress.com/2011/06/12/ruby-vs-python-2011/

Python vs. Ruby for metaprogramming [closed]

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I'm currently primarily a D programmer and am looking to add another language to my toolbox, preferably one that supports the metaprogramming hacks that just can't be done in a statically compiled language like D.
I've read up on Lisp a little and I would love to find a language that allows some of the cool stuff that Lisp does, but without the strange syntax, etc. of Lisp. I don't want to start a language flame war, and I'm sure both Ruby and Python have their tradeoffs, so I'll list what's important to me personally. Please tell me whether Ruby, Python, or some other language would be best for me.
Important:
Good metaprogramming. Ability to create classes, methods, functions, etc. at runtime. Preferably, minimal distinction between code and data, Lisp style.
Nice, clean, sane syntax and consistent, intuitive semantics. Basically a well thought-out, fun to use, modern language.
Multiple paradigms. No one paradigm is right for every project, or even every small subproblem within a project.
An interesting language that actually affects the way one thinks about programming.
Somewhat important:
Performance. It would be nice if performance was decent, but when performance is a real priority, I'll use D instead.
Well-documented.
Not important:
Community size, library availability, etc. None of these are characteristics of the language itself, and all can change very quickly.
Job availability. I am not a full-time, professional programmer. I am a grad student and programming is tangentially relevant to my research.
Any features that are primarily designed with very large projects worked on by a million code monkeys in mind.
I've read up on Lisp a little and I would love to find a language that allows some of the cool stuff that Lisp does, but without the strange syntax, etc. of Lisp.
Wouldn't we all.
minimal distinction between code and data, Lisp style
Sadly, the minimal distinction between code and data and "strange" syntax are consequences of each other.
If you want easy-to-read syntax, you have Python. However, the code is not represented in any of the commonly-used built-in data structures. It fails—as most languages do—in item #1 of your 'important' list. That makes it difficult to provide useful help.
You can't have it all. Remember, you aren't the first to have this thought. If something like your ideal language existed, we'd all be using it. Since the real world falls short of your ideals, you'll have to re-prioritize your wish list. The "important" section has to be rearranged to identify what's really important to you.
Honestly, as far as metaprogramming facilities go, Ruby and Python are a lot more similar than some of their adherent like to admit. This review of both language offers a pretty good comparison/review:
http://regebro.wordpress.com/2009/07/12/python-vs-ruby/
So, just pick one based on some criteria. Maybe you like Rails and want to study that code. Maybe SciPy is your thing. Look at the ecosystem of libraries, community, etc, and pick one. You certainly won't lose out on some metaprogramming nirvana based on your choice of either.
Disclaimer: I only dabble in either language, but I have at least written small working programs (not just quick scripts, for which I use Perl, bash or GNU make) in both.
Ruby can be really nice for the "multiple paradigms" point 3, because it works hard to make it easy to create domain-specific languages. For example, browse online and look at a couple of bits of Ruby on Rails code, and a couple of bits of Rake code. They're both Ruby, and you can see the similarities, but they don't look like what you'd normally think of as the same language.
Python seems to me to be a bit more predictable (possibly correlated to 'clean' and 'sane' point 2), but I don't really know whether that's because of the language itself or just that it's typically used by people with different values. I have never attempted deep magic in Python. I would certainly say that both languages are well thought out.
Both score well in 1 and 4. [Edit: actually 1 is pretty arguable - there is "eval" in both, as common in interpreted languages, but they're hardly conceptually pure. You can define closures, assign methods to objects, and whatnot. Not sure whether this goes as far as you want.]
Personally I find Ruby more fun, but in part that's because it's easier to get distracted thinking of cool ways to do things. I've actually used Python more. Sometimes you don't want cool, you want to get on with it so it's done before bedtime...
Neither of them is difficult to get into, so you could just decide to do your next minor task in one, and the one after that in the other. Or pick up an introductory book on each from the library, skim-read them both and see what grabs you.
There's not really a huge difference between python and ruby at least at an ideological level. For the most part, they're just different flavors of the same thing. Thus, I would recommend seeing which one matches your programming style more.
Have you considered Smalltalk? It offers a very simple, clear and extensible syntax with reflectivity and introspection capabilities and a fully integrated development environment that takes advantage of those capabilities. Have a look at some of the work being done in Squeak Smalltalk for instance. A lot of researchers using Squeak hang out on the Squeak mailing list and #squeak on freenode, so you can get help on complex issues very easily.
Other indicators of its current relevance: it runs on any platform you'd care to name (including the iPhone); Gilad Bracha is basing his Newspeak work on Squeak; the V8 team cut their teeth on Smalltalk VMs; and Dan Ingalls and Randal Schwartz have recently returned to Smalltalk work after years in the wilderness.
Best of luck with your search - let us know what you decide in the end.
Lisp satisfies all your criteria, including performance, and it is the only language that doesn't have (strange) syntax. If you eschew it on such an astoundingly ill-informed/wrong-headed basis and consequently miss out on the experience of using e.g. Emacs+SLIME+CL, you'll be doing yourself a great disservice.
Your 4 "important" points lead to Ruby exactly, while the 2 "somewhat important" points ruled by Python. So be it.
You are describing Ruby.
Good metaprogramming. Ability to create classes, methods, functions,
etc. at runtime. Preferably, minimal
distinction between code and data,
Lisp style.
It's very easy to extend and modify existing primitives at runtime. In ruby everything is an object, strings, integers, even functions.
You can also construct shortcuts for syntactic sugar, for example with class_eval.
Nice, clean, sane syntax and consistent, intuitive semantics.
Basically a well thought-out, fun to
use, modern language.
Ruby follows the principle of less surprise, and when comparing Ruby code vs the equivalent in other language many people consider it more "beautiful".
Multiple paradigms. No one paradigm is right for every project,
or even every small subproblem within
a project.
You can follow imperative, object oriented, functional and reflective.
An interesting language that actually affects the way one thinks
about programming.
That's very subjective, but from my point of view the ability to use many paradigms at the same time allows for very interesting ideas.
I've tried Python and it doesn't fit your important points.
Compare code examples that do the same thing (join with a newline non-empty descriptions of items from a myList list) in different languages (languages are arranged in reverse-alphabetic order):
Ruby:
myList.collect { |f| f.description }.select { |d| d != "" }.join("\n")
Or
myList.map(&:description).reject(&:empty?).join("\n")
Python:
descriptions = (f.description() for f in mylist)
"\n".join(filter(len, descriptions))
Or
"\n".join(f.description() for f in mylist if f.description())
Perl:
join "\n", grep { $_ } map { $_->description } #myList;
Or
join "\n", grep /./, map { $_->description } #myList;
Javascript:
myList.map(function(e) e.description())
.filter(function(e) e).join("\n")
Io:
myList collect(description) select(!="") join("\n")
Here's an Io guide.
Ruby would be better than Lisp in terms of being "mainstream" (whatever that really means, but one realistic concern is how easy it would be to find answers to your questions on Lisp programming if you were to go with that.) In any case, I found Ruby very easy to pick up. In the same amount of time that I had spent first learning Python (or other languages for that matter), I was soon writing better code much more efficiently than I ever had before. That's just one person's opinion, though; take it with a grain of salt, I guess. I know much more about Ruby at this point than I do Python or Lisp, but you should know that I was a Python person for quite a while before I switched.
Lisp is definitely quite cool and worth looking into; as you said, the size of community, etc. can change quite quickly. That being said, the size itself isn't as important as the quality of the community. For example, the #ruby-lang channel is still filled with some incredibly smart people. Lisp seems to attract some really smart people too. I can't speak much about the Python community as I don't have a lot of firsthand experience, but it seems to be "too big" sometimes. (I remember people being quite rude on their IRC channel, and from what I've heard from friends that are really into Python, that seems to be the rule rather than the exception.)
Anyway, some resources that you might find useful are:
1) The Pragmatic Programmers Ruby Metaprogramming series (http://www.pragprog.com/screencasts/v-dtrubyom/the-ruby-object-model-and-metaprogramming) -- not free, but the later episodes are quite intriguing. (The code is free, if you want to download it and see what you'd be learning about.)
2) On Lisp by Paul Graham (http://www.paulgraham.com/onlisp.html). It's a little old, but it's a classic (and downloadable for free).
#Jason I respectively disagree. There are differences that make Ruby superior to Python for metaprogramming - both philosophical and pragmatic. For starters, Ruby gets inheritance right with Single Inheritance and Mixins. And when it comes to metaprogramming you simply need to understand that it's all about the self. The canonical difference here is that in Ruby you have access to the self object at runtime - in Python you do not!
Unlike Python, in Ruby there is no separate compile or runtime phase. In Ruby, every line of code is executed against a particular self object. In Ruby every class inherits from both object and a hidden metaclass. This makes for some interesting dynamics:
class Ninja
def rank
puts "Orange Clan"
end
self.name #=> "Ninja"
end
Using self.name accesses the Ninja classes' metaclass name method to return the class name of Ninja. Does metaprogramming flower so beautiful in Python? I sincerely doubt it!
I am using Python for many projects and I think Python does provide all the features you asked for.
important:
Metaprogramming: Python supports metaclasses and runtime class/method generation etc
Syntax: Well thats somehow subjective. I like Pythons syntax for its simplicity, but some People complain that Python is whitespace-sensitive.
Paradigms: Python supports procedural, object-oriented and basic functional programming.
I think Python has a very practical oriented style, it was very inspiring for me.
Somewhat important:
Performance: Well its a scripting language. But writing C extensions for Python is a common optimization practice.
Documentation: I cannot complain. Its not that detailed as someone may know from Java, but its good enough.
As you are grad student you may want to read this paper claiming that Python is all a scientist needs.
Unfortunately I cannot compare Python to Ruby, since I never used that language.
Regards,
Dennis
Well, if you don't like the lisp syntax perhaps assembler is the way to go. :-)
It certainly has minimal distinction between code and data, is multi-paradigm (or maybe that is no-paradigm) and it's a mind expanding (if tedious) experience both in terms of the learning and the tricks you can do.
Io satisfies all of your "Important" points. I don't think there's a better language out there for doing crazy meta hackery.
one that supports the metaprogramming hacks that just can't be done in a statically compiled language
I would love to find a language that allows some of the cool stuff that Lisp does
Lisp can be compiled.
Did you try Rebol?
My answer would be neither. I know both languages, took a class on Ruby and been programming in python for several years. Lisp is good at metaprogramming due to the fact that its sole purpose is to transform lists, its own source code is just a list of tokens so metaprogramming is natural. The three languages I like best for this type of thing is Rebol, Forth and Factor. Rebol is a very strong dialecting language which takes code from its input stream, runs an expression against it and transforms it using rules written in the language. Very expressive and extremely good at dialecting. Factor and Forth are more or less completely divorced from syntax and you program them by defining and calling words. They are generally mostly written in their own language. You don't write applications in traditional sense, you extend the language by writing your own words to define your particular application. Factor can be especially nice as it has many features I have only seen in smalltalk for evaluating and working with source code. A really nice workspace, interactive documents, etc.
There isn't really a lot to separate Python and Ruby. I'd say the Python community is larger and more mature than the Ruby community, and that's really important for me. Ruby is a more flexible language, which has positive and negative repercussions. However, I'm sure there will be plenty of people to go into detail on both these languages, so I'll throw a third option into the ring. How about JavaScript?
JavaScript was originally designed to be Scheme for the web, and it's prototype-based, which is an advantage over Python and Ruby as far as multi-paradigm and metaprogramming is concerned. The syntax isn't as nice as the other two, but it is probably the most widely deployed language in existence, and performance is getting better every day.
If you like the lisp-style code-is-data concept, but don't like the Lispy syntax, maybe Prolog would be a good choice.
Whether that qualifies as a "fun to use, modern language", I'll leave to others to judge. ;-)
Ruby is my choice after exploring Python, Smalltalk, and Ruby.
What about OCaml ?
OCaml features: a static type system, type inference, parametric polymorphism, tail recursion, pattern matching, first class lexical closures, functors (parametric modules), exception handling, and incremental generational automatic garbage collection.
I think that it satisfies the following:
Important:
Nice, clean, sane syntax and consistent, intuitive semantics. Basically a well thought-out, fun to use, modern language.
Multiple paradigms. No one paradigm is right for every project, or even every small subproblem within a project.
An interesting language that actually affects the way one thinks about programming.
Somewhat important:
Performance. It would be nice if performance was decent, but when performance is a real priority, I'll use D instead.
Well-documented.
I've use Python a very bit, but much more Ruby. However I'd argue they both provide what you asked for.
If I see all your four points then you may at least check:
http://www.iolanguage.com/
And Mozart/Oz may be interesting for you also:
http://mozart.github.io/
Regards
Friedrich
For python-style syntax and lisp-like macros (macros that are real code) and good DSL see converge.
I'm not sure that Python would fulfill all things you desire (especially the point about the minimal distinction between code and data), but there is one argument in favour of python. There is a project out there which makes it easy for you to program extensions for python in D, so you can have the best of both worlds. http://pyd.dsource.org/celerid.html
if you love the rose, you have to learn to live with the thorns :)
I would recommend you go with Ruby.
When I first started to learn it, I found it really easy to pick up.
Do not to mix Ruby Programming Language with Ruby Implementations, thinking that POSIX threads are not possible in ruby.
You can simply compile with pthread support, and this was already possible at the time this thread was created, if you pardon the pun.
The answer to this question is simple. If you like lisp, you will probably prefer ruby. Or, whatever you like.
I suggest that you try out both languages and pick the one that appeals to you. Both Python and Ruby can do what you want.
Also read this thread.
Go with JS just check out AJS (Alternative JavaScript Syntax) at my github http://github.com/visionmedia it will give you some cleaner looking closures etc :D
Concerning your main-point (meta-programming):
Version 1.6 of Groovy has AST (Abstract Syntax Tree) programming built-in as a standard and integrated feature.
Ruby has RubyParser, but it's an add-on.

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