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We have a sizable code base in Perl. For the forseeable future, our codebase will remain in Perl. However, we're looking into adding a GUI-based dashboard utility. We are considering writing the dashboard in Python (using tkinter or wx). The problem, however, is that we would like to leverage our existing Perl codebase in the Python GUI.
So... any suggestions on how achieve this? We are considering a few options:
Write executables (in Perl) that mimic function calls; invoke those Perl executables in python as system calls.
Write Perl executables on-the-fly inside the Python dashboard, and invoke the (temporary) Perl executable.
Find some kind of Perl-to-Python converter or binding.
Any other ideas? I'd love to hear if other people have confronted this problem. Unfortunately, it's not an option to convert the codebase itself to Python at this time.
I hate to be another one in the chorus, but...
Avoid the use of an alternate language
Use Wx so it's native look and feel makes the application look "real" to non-technical audiences.
Download the Padre source code and see how it does Wx Perl code, then steal rampantly from it's best tricks or maybe just gut it and use the application skeleton (using the Artistic half of the Perl dual license to make it legal).
Build your own Strawberry Perl subclass to package the application as an MSI installer and push it out across the corporate Active Directory domain.
Of course, I only say all this because you said "Dashboard" which I read as "Corporate", which then makes me assume a Microsoft AD network...
You can spawn a child process and use an IPC mechanism like sockets or STDIO, or even embed one interpreter in the other.
But why switch languages when Perl offers several Tk (Tk, Tkx, and Tcl::Tk) bindings and a very capable Wx binding?
I have written and distributed GUI projects with Perl's Tk and Wx libraries.
If you are need the ability to create stand-alone executables, check out PAR::Packer, ActiveState's PerlApp, and Cava Pacakger.
Try the CPAN distribution Python (pyperl) for interfacing with python code.
Well, if you really want to write the GUI in another language (which, seriously, is just a bad idea, since it will cost you more than it could ever benefit you), the thing you should do is the following:
Document your Perl app in terms of the services it provides. You should do it with XML Schema Definition - XSD - for the data types and Web Service Description Language - WSDL - for the actual service.
Implement the services in Perl, possibly using Catalyst::Controller::SOAP, or just XML::Compile::SOAP.
Consume the services from your whatever-language GUI interface.
Profit.
But honestly, I really suggest you taking a look at the Perl GTK2 binding, it is awesome, including features such as implementing a Gtk class entirely in Perl and using it as argument to a function written in C - for instance, you can write a model class for a gtk tree entirely in Perl.
I'd avoid inter-language calls if possible; fragility and massive increases in dependencies await you down this road. However, there is...
Inline::Python
If python must be used, the Inline::* series of modules have been generally well received. This lets you write python inside a perl script. You still have to write perl but it would let you use python libraries inside perl scripts. It will make things more difficult to debug, though.
I'd think the major criterion for any qualified answer would involve the details of the existing codebase. How is this Perl code called and how does it return it's results?
A collection of command line utilities returning results through reasonably good textual output ("good" as in "amenable to further machine parsing" or "pipeline friendly") ... should be reasonably easy to call from any programming language (and Python's excellent subprocess and multiprocessing modules in particular). A collection of web CGI or other modules layered between Apache and some DBMS system could still be accessed with things like urlopen2 or mechanize -- but it might be better to bypass the Perl code and write Python to query the underlying (presumably canonical) model (data store).
If the majority of the codebase is a set of libraries or modules ... and the functionality that your proposed dashboard requires isn't already exposed via some higher level mechanism (some command line interface, networking protocol, etc) ... then it's basically insane to consider interfacing to it through any language other than Perl. (Unless, by some strange and extremely unlikely twist of fate, your existing codebase and your intended implementation target are both already stable under Parrot).
Let's ask a different, broader, question: What interface to you intend to use between your dashboard and your existing code base?
This question is paramount regardless of your choice of implementation language. If you write the dashboard in Perl it still needs to call into your existing code base in some way. You probably need to fix-up your code base to implement support for whatever your going to use for your dashboard. At the point where your codebase supports the necessary API (has command line or IPC protocol calls into the desired functionality which return results over any reasonable IPC mechanism) ... then your choice of dashboard implementation language will be essentially arbitrary.
Interesting project: I would opt for loose-coupling and consider an XML-RPC or JSON based approach.
Find some kind of Perl-to-Python converter
Try out my pythonizer - it does a pretty good job at that!
There is a project I'm about to build in Smalltalk (Pharo). And there is a python library which I intend to use for the same. Now, there are 3 options:
Smalltalk wrapper for those python libraries
Porting the python library to Smalltalk
Write the library from scratch (in Smalltalk) for use in my project
The following are my queries:
What are 'basic' differences in porting/wrapping (No satisfactory explanation found anywhere yet)
How to know when to use which (of all the three)?
Any resources or pointers where I can get further help/some kick-start into my project.
Thanks!
Wrapper
Write functions in the native language whose sole purpose is to call the functions in the external library. The goal is to do as little as possible in the native language. For example, translating data types from the native language to the external library language, etc.
Wrappers make sense when the external library is:
written in a more efficient language than the native code (eg, a C++ library called from Python)
large/complex and would be time-consuming or error prone to translate
regularly updated; in a well-maintained library the interfaces (what your wrapper is concerned with) will change less often than the implementation of the features; so if you have wrappers around the functionality, updating to a new version of the library should be fairly straightforward
Porting
A port is simply a translation from one language to another. In general, the same logic is maintained as much as possible.
Porting makes sense when:
the native language is more efficient than the external library
the library is simple and one wants to save on the overhead involved with wrapping
one intends to make and maintain changes to the ported code in the native language
there are no plans to use the external library in its own language
one wants to learn one or both of the languages involved
Re-Write
Think of a Re-Write as a Port with a lot of refactoring. The goal is to take advantage of features of the native language to improve the library in some way (efficiency, readability, etc.)
Re-Writing makes sense in all of the same scenarios as porting. Deciding whether to do a simple port or a full re-write usually comes down to one question:
Is there a better way to implement the features of the external library in the native language?
I need to generate C structs and arrays from data stored in a db table, and alternately parse similar info. I use both ruby and python for this task, and was wondering if anyone heard of a module/lib that handles this for either/both languages? I could do this on my own with some string processing, but wanted to check if there's a known and tested parser out there that people know of. thanks.
Check out open-source software tool SWIG (Simplified Wrapper and Interface Generator). First sentence of the intro on the webpage:
SWIG is a software development tool
that connects programs written in C
and C++ with a variety of high-level
programming languages. SWIG is used
with different types of languages
including common scripting languages
such as Perl, PHP, Python, Tcl and
Ruby.
Very mature (initial release - February 1996 according to Wikipedia) and there are lots of tutorials, documentation, and help.
There is a basic C struct parser here on the pyparsing wiki. Pyparsing is a Python module for creating parsers by assembling separate parsing building blocks together. (No help on the Ruby part of the question, though.)
Haven't used it myself, but CAST might be worth a look:
http://cast.rubyforge.org/
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Considering the criteria listed below, which of Python, Groovy or Ruby would you use?
Criteria (Importance out of 10, 10 being most important)
Richness of API/libraries available (eg. maths, plotting, networking) (9)
Ability to embed in desktop (java/c++) applications (8)
Ease of deployment (8)
Ability to interface with DLLs/Shared Libraries (7)
Ability to generate GUIs (7)
Community/User support (6)
Portability (6)
Database manipulation (3)
Language/Semantics (2)
I think it's going to be difficult to get an objective comparison. I personally prefer Python. To address one of your criteria, Python was designed from the start to be an embeddable language. It has a very rich C API, and the interpreter is modularized to make it easy to call from C. If Java is your host environment, you should look at Jython, an implementation of Python inside the Java environment (VM and libs).
Having worked with all 3 of them, this is what I can say:
Python
has very mature libraries
libraries are documented
documentation can be accessed from your debugger/shell at runtime through the docstrings
you can develop code without an IDE
Ruby
has some great libraries ( even though some are badly documented )
Ruby's instrospection mechanisms are great. They make writing code pretty easy ( even if documentation is not available )
you can develop code without an IDE
Groovy
you can benefit from everything Java has to offer
syntax is somewhat inspired from Ruby
it's hard to write code without an IDE. You have no way to debug stuff from your console ( this is something you can easily do in Python/Ruby ) and the available Groovy plugins have a lot of catching up to do. I wrote some apps using Groovy and as they get bigger I regret not going with Ruby/Python ( debugging would have been WAY more easier ). If you'll only develop from an IDE, Groovy's a cool language.
Just to muddy the waters...
Groovy give you access to Java. Java has an extremely rich set of APIs/Libraries, applications, etc.
Groovy is embeddable, although easiest in Java.
DLLs/Libraries (if you're talking about non-Groovy/Java) may be somewhat problematic, although there are ways and some APIs to help.
I've done some Python programming, but being more familiar with Java, Groovy comes a lot easier to me.
Groovy? I'm just picking it up; try this (inside the groovyconsole):
File.metaClass.invokeMethod = { String name, args ->
System.out.print ("Call to $name intercepted...");
File.metaClass.getMetaMethod(name, args).invoke(delegate, args);
}
new File("c:/temp").eachFile{
if (it.isFile()) println it.canonicalPath
}
The first code is AOP. All calls to any method of File object will be intercepted. No additional tools required. This is executed against existing Java class dynamically.
In the second block, you remove the 'f' closure parameter. Being just one parameter, it defaults to the built in "it" variable available to the closure context.
Here is what you get:
"Call to isFile intercepted...C:\temp\img.jpg"
etc.
try Groovy .. it has all features that you need there. You can use existing java lib without any modification on its classes.
basically .. groovy is java++, it is more dynamic and fun to learn (just like ruby)
I dont like ruby or python syntax so I will put them behind. Groovy is just like C/C++ syntax so I like him lol :)
Python has all nine criteria. It scores a 56.
I'm sure Ruby has everything Python has. It seems to have fewer libraries. So it scores a 51.
I don't know if Groovy has every feature.
Since Python is 56 and Ruby is a 51, Python just barely edges out Ruby.
However, I think this kind of decision can still boil down to some subjective issues outside these nine criteria.
From your critera, I'd pick JRuby:
Richness of API/libraries available (eg. maths, plotting, networking) (9)
Everything the JVM has access to, which is a lot
Ability to embed in desktop (java/c++) applications (8)
Excellent Monkeybars framework, which lets you design a swing GUI in your GUI designer, and then wire it up using clean ruby code
Ease of deployment (8)
Rawr can package your app as an executable jar
Ability to interface with DLLs/Shared Libraries (7)
Java shared libraries easily, C ones via jna + libffi
Ability to generate GUIs (7)
Swing just works. Not sure how easy it is to use QtJambi, but it's definitely possible.
Community/User support (6)
Lots. Ruby has an excellent community.
Portability (6)
Everywhere the JVM works
Database manipulation (3)
All the ruby database libraries and all the java ones
Language/Semantics (2)
Here's where ruby takes the definite lead over groovy and python. The language has had some really beautiful design decisions taken early on, which shows up in the consistency and power of the standard library. Blocks, in particular, make it a joy to use.
This sort of adding-up-scores-by-features is not a good way to choose a programming language. You'd be better off choosing whichever you know the best. If you don't know any of them, try them out for a little while. If you have a really specific project in mind, then maybe some programming languages would be better, but if you just have general preferences you will never come to a consensus.
That said, Python is pretty flexible, it's the most popular on your list so the easiest to solve whatever sorts of problems you have by searching, so I'd recommend Python.
Perl? Yikes.
As someone has observed Perl is like a big explosion in a punctuation factory. It's terseness is not an advantage if the resultant code is not self documenting.
Have used Groovy for some utility tasks, easy to get going. Full access to Java libraries, plus some cool addtions to it, like listing the files in a directory using a closure:
// process all files printing out full name (. and .. auto excluded)
new File(basedir).eachFile{ f->
if (f.isFile()) println f.canonicalPath
}
I know it's not on your list, but at least look at perl.
Richness of Api/Libraries to sink a ship.
Runs on more systems than most people realise exists.
Works well with Binary libraries.
Has a huge community.
Portability, See above.
Database manipulation: more ways to do it. ( Pick your favorite module )
And one of the most expressive/terse languages around.
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Right now I'm developing mostly in C/C++, but I wrote some small utilities in Python to automatize some tasks and I really love it as language (especially the productivity).
Except for the performances (a problem that could be sometimes solved thanks to the ease of interfacing Python with C modules), do you think it is proper for production use in the development of stand-alone complex applications (think for example to a word processor or a graphic tool)?
What IDE would you suggest? The IDLE provided with Python is not enough even for small projects in my opinion.
We've used IronPython to build our flagship spreadsheet application (40kloc production code - and it's Python, which IMO means loc per feature is low) at Resolver Systems, so I'd definitely say it's ready for production use of complex apps.
There are two ways in which this might not be a useful answer to you :-)
We're using IronPython, not the more usual CPython. This gives us the huge advantage of being able to use .NET class libraries. I may be setting myself up for flaming here, but I would say that I've never really seen a CPython application that looked "professional" - so having access to the WinForms widget set was a huge win for us. IronPython also gives us the advantage of being able to easily drop into C# if we need a performance boost. (Though to be honest we have never needed to do that. All of our performance problems to date have been because we chose dumb algorithms rather than because the language was slow.) Using C# from IP is much easier than writing a C Extension for CPython.
We're an Extreme Programming shop, so we write tests before we write code. I would not write production code in a dynamic language without writing the tests first; the lack of a compile step needs to be covered by something, and as other people have pointed out, refactoring without it can be tough. (Greg Hewgill's answer suggests he's had the same problem. On the other hand, I don't think I would write - or especially refactor - production code in any language these days without writing the tests first - but YMMV.)
Re: the IDE - we've been pretty much fine with each person using their favourite text editor; if you prefer something a bit more heavyweight then WingIDE is pretty well-regarded.
You'll find mostly two answers to that – the religous one (Yes! Of course! It's the best language ever!) and the other religious one (you gotta be kidding me! Python? No... it's not mature enough). I will maybe skip the last religion (Python?! Use Ruby!). The truth, as always, is far from obvious.
Pros: it's easy, readable, batteries included, has lots of good libraries for pretty much everything. It's expressive and dynamic typing makes it more concise in many cases.
Cons: as a dynamic language, has way worse IDE support (proper syntax completion requires static typing, whether explicit in Java or inferred in SML), its object system is far from perfect (interfaces, anyone?) and it is easy to end up with messy code that has methods returning either int or boolean or object or some sort under unknown circumstances.
My take – I love Python for scripting, automation, tiny webapps and other simple well defined tasks. In my opinion it is by far the best dynamic language on the planet. That said, I would never use it any dynamically typed language to develop an application of substantial size.
Say – it would be fine to use it for Stack Overflow, which has three developers and I guess no more than 30k lines of code. For bigger things – first your development would be super fast, and then once team and codebase grow things are slowing down more than they would with Java or C#. You need to offset lack of compilation time checks by writing more unittests, refactorings get harder cause you never know what your refacoring broke until you run all tests or even the whole big app, etc.
Now – decide on how big your team is going to be and how big the app is supposed to be once it is done. If you have 5 or less people and the target size is roughly Stack Overflow, go ahead, write in Python. You will finish in no time and be happy with good codebase. But if you want to write second Google or Yahoo, you will be much better with C# or Java.
Side-note on C/C++ you have mentioned: if you are not writing performance critical software (say massive parallel raytracer that will run for three months rendering a film) or a very mission critical system (say Mars lander that will fly three years straight and has only one chance to land right or you lose $400mln) do not use it. For web apps, most desktop apps, most apps in general it is not a good choice. You will die debugging pointers and memory allocation in complex business logic.
In my opinion python is more than ready for developing complex applications. I see pythons strength more on the server side than writing graphical clients. But have a look at http://www.resolversystems.com/. They develop a whole spreadsheet in python using the .net ironpython port.
If you are familiar with eclipse have a look at pydev which provides auto-completion and debugging support for python with all the other eclipse goodies like svn support. The guy developing it has just been bought by aptana, so this will be solid choice for the future.
#Marcin
Cons: as a dynamic language, has way
worse IDE support (proper syntax
completion requires static typing,
whether explicit in Java or inferred
in SML),
You are right, that static analysis may not provide full syntax completion for dynamic languages, but I thing pydev gets the job done very well. Further more I have a different development style when programming python. I have always an ipython session open and with one F5 I do not only get the perfect completion from ipython, but object introspection and manipulation as well.
But if you want to write second Google
or Yahoo, you will be much better with
C# or Java.
Google just rewrote jaiku to work on top of App Engine, all in python. And as far as I know they use a lot of python inside google too.
I really like python, it's usually my language of choice these days for small (non-gui) stuff that I do on my own.
However, for some larger Python projects I've tackled, I'm finding that it's not quite the same as programming in say, C++. I was working on a language parser, and needed to represent an AST in Python. This is certainly within the scope of what Python can do, but I had a bit of trouble with some refactoring. I was changing the representation of my AST and changing methods and classes around a lot, and I found I missed the strong typing that would be available to me in a C++ solution. Python's duck typing was almost too flexible and I found myself adding a lot of assert code to try to check my types as the program ran. And then I couldn't really be sure that everything was properly typed unless I had 100% code coverage testing (which I didn't at the time).
Actually, that's another thing that I miss sometimes. It's possible to write syntactically correct code in Python that simply won't run. The compiler is incapable of telling you about it until it actually executes the code, so in infrequently-used code paths such as error handlers you can easily have unseen bugs lurking around. Even code that's as simple as printing an error message with a % format string can fail at runtime because of mismatched types.
I haven't used Python for any GUI stuff so I can't comment on that aspect.
Python is considered (among Python programmers :) to be a great language for rapid prototyping. There's not a lot of extraneous syntax getting in the way of your thought processes, so most of the work you do tends to go into the code. (There's far less idioms required to be involved in writing good Python code than in writing good C++.)
Given this, most Python (CPython) programmers ascribe to the "premature optimization is the root of all evil" philosophy. By writing high-level (and significantly slower) Python code, one can optimize the bottlenecks out using C/C++ bindings when your application is nearing completion. At this point it becomes more clear what your processor-intensive algorithms are through proper profiling. This way, you write most of the code in a very readable and maintainable manner while allowing for speedups down the road. You'll see several Python library modules written in C for this very reason.
Most graphics libraries in Python (i.e. wxPython) are just Python wrappers around C++ libraries anyway, so you're pretty much writing to a C++ backend.
To address your IDE question, SPE (Stani's Python Editor) is a good IDE that I've used and Eclipse with PyDev gets the job done as well. Both are OSS, so they're free to try!
[Edit] #Marcin: Have you had experience writing > 30k LOC in Python? It's also funny that you should mention Google's scalability concerns, since they're Python's biggest supporters! Also a small organization called NASA also uses Python frequently ;) see "One coder and 17,000 Lines of Code Later".
Nothing to add to the other answers, besides that if you choose python you must use something like pylint which nobody mentioned so far.
One way to judge what python is used for is to look at what products use python at the moment. This wikipedia page has a long list including various web frameworks, content management systems, version control systems, desktop apps and IDEs.
As it says here - "Some of the largest projects that use Python are the Zope application server, YouTube, and the original BitTorrent client. Large organizations that make use of Python include Google, Yahoo!, CERN and NASA. ITA uses Python for some of its components."
So in short, yes, it is "proper for production use in the development of stand-alone complex applications". So are many other languages, with various pros and cons. Which is the best language for your particular use case is too subjective to answer, so I won't try, but often the answer will be "the one your developers know best".
Refactoring is inevitable on larger codebases and the lack of static typing makes this much harder in python than in statically typed languages.
And as far as I know they use a lot of python inside google too.
Well i'd hope so, the maker of python still works at google if i'm not mistaken?
As for the use of Python, i think it's a great language for stand-alone apps. It's heavily used in a lot of Linux programs, and there are a few nice widget sets out there to aid in the development of GUI's.
Python is a delight to use. I use it routinely and also write a lot of code for work in C#. There are two drawbacks to writing UI code in Python. one is that there is not a single ui framework that is accepted by the majority of the community. when you write in c# the .NET runtime and class libraries are all meant to work together. With Python every UI library has at's own semantics which are often at odds with the pythonic mindset in which you are trying to write your program. I am not blaming the library writers. I've tried several libraries (wxwidgets, PythonWin[Wrapper around MFC], Tkinter), When doing so I often felt that I was writing code in a language other than Python (despite the fact that it was python) because the libraries aren't exactly pythonic they are a port from another language be it c, c++, tk.
So for me I will write UI code in .NET (for me C#) because of the IDE & the consistency of the libraries. But when I can I will write business logic in python because it is more clear and more fun.
I know I'm probably stating the obvious, but don't forget that the quality of the development team and their familiarity with the technology will have a major impact on your ability to deliver.
If you have a strong team, then it's probably not an issue if they're familiar. But if you have people who are more 9 to 5'rs who aren't familiar with the technology, they will need more support and you'd need to make a call if the productivity gains are worth whatever the cost of that support is.
I had only one python experience, my trash-cli project.
I know that probably some or all problems depends of my inexperience with python.
I found frustrating these things:
the difficult of finding a good IDE for free
the limited support to automatic refactoring
Moreover:
the need of introduce two level of grouping packages and modules confuses me.
it seems to me that there is not a widely adopted code naming convention
it seems to me that there are some standard library APIs docs that are incomplete
the fact that some standard libraries are not fully object oriented annoys me
Although some python coders tell me that they does not have these problems, or they say these are not problems.
Try Django or Pylons, write a simple app with both of them and then decide which one suits you best. There are others (like Turbogears or Werkzeug) but those are the most used.