I have written a bunch of Perl libraries (actually Perl classes) and I want to use some of them in my Python application. Is there a natural way to do this without using SWIG or writing Perl API for Python. I am asking for a similar way of PHP's Perl interface. If there is no such kind of work for Perl in Python. What is the easiest way to use Perl classes in python?
Personally, I would expose the Perl libs as services via XML/RPC or some other such mechanism. That way you can call them from your Python application in a very natural manner.
I haven't tried it, but Inline::Python lets you call Python from Perl.
You should be able to use a thin bit of perl to load your python app and then use the perl python package that comes with I::P to access your Perl objects.
"What is the easiest way to use Perl classes in python?"
Easiest. Rewrite the Perl into Python and be done with it. Seriously. Just pick one language—that's easiest. Leaving Perl behind is no great loss. Rewriting classes into Python may give you an opportunity to improve them in small ways.
Not so easy. Run the Perl application using Python's subprocess module. That uses the Perl classes in the Perl application without problems. You can easily create pipelines so the Perl gets input from Python and produces output to Python
someApp.py | something.pl | finalStep.py
This has the advantage of breaking your application into three concurrent processes, using up lots of processor resources and running (sometimes) in 1/3 the time.
Everything else is much less easy.
You've just missed a chance for having Python running on the Parrot VM together with Perl. On April 1st, 2009 PEP 401 was published, and one of the Official Acts of the FLUFL read:
Recognized that C is a 20th century language with almost universal rejection by programmers under the age of 30, the CPython implementation will terminate with the release of Python 2.6.2 and 3.0.2. Thereafter, the reference implementation of Python will target the Parrot virtual machine. Alternative implementations of Python (e.g. Jython, IronPython, and PyPy ) are officially discouraged but tolerated.
Check out PyPerl.
WARNING: PyPerl is currently unmaintained, so don't use it if you require stability.
Related
Is there any good way to call python from clojure as a means of doing data science with scipy, numpy, scikit-learn, etc.
I know about implementations of clojure which run on python instead of java, but this doeesn't work for me, as I also need to call java libraries in my project. I also know about Jython, but I don't know of a clean way to use this with Clojure.
I want to use Clojure in my projects because I prefer it as a language, but I can't deny that Python has an incredible community, and some of the most beautiful, well-designed libraries around.
Instead of trying to get Jython to play well with both Clojure and numpy/scipy, you can use Hy. It is hosted on Python and it somewhat resembles Clojure.
If I really wanted to use numpy/scipy, I would write the backend in Python (or Hy), run it as a separate service. And if I really like ring for instance, or can't live without Instaparse, I would write a frontend in Clojure.
As an aside Python has EDN libs. It would be an interesting project to integrate one of them in Hy, or write one from scratch.
Give the toolz library a try, it's a functional standard library for Python that was designed to generally adhere to the API of the Clojure standard library.
Apart from that, I'd encourage you to find the seams between your computations, and write individual tools in the Unix way in either Clojure or Python depending on which seems to fit that use case best. Serialize data between the tools, either as text/JSON through pipes or using a binary serialization format like Protobuf, which has standard APIs for both Java and Python.
If you had a gun to my head and told me to build Clojure/Python interop, I'd start with py4j and bridge the two languages through Java interfaces, using implements members in a Python class and reify on the Clojure side.
You could use Graal VM now. Although some large companies are using it in production, it's still early days. Here's an example of using Python from Clojure:
(.eval context "python" "
import time;
time.clock()
")
http://gigasquidsoftware.com/blog/2017/10/22/embedded-interop-between-clojure-r-and-python-with-graalvm/
I'll preface this by saying I am quite new to PyPy, though fairly experienced with Python.
I'm looking to run a web app where I run untrusted Python code. The PyPy sandboxing features look ideal for what I'm doing.
The PyPy docs on sandboxing indicate that you can call a PyPy sandbox from either Python or PyPy. This seems to imply that there's some separate program or executable that is the sandbox.
I'm wondering, is it possible to call a PyPy sandbox from a non-Python language? I'm looking at Haskell in particular, but it's also very possible that I could use C or C++ as an intermediate.
Yes, that's possible. The PyPy sandbox is a separate process communicating only via stdin/stdout. If you want to rewrite the "external" part, you can; it's not using anything that should be too heavily Python-related.
Note that the sandboxing feature of PyPy is not being maintained any more, see http://www.pypy.org/features.html#sandboxing
If I learn Jython first, does that mean I will also be learning all of the Python language? When I say all, I mean all the basic constructs of the language, nothing else. What will I not learn about Python or CPython, if I start with Jython? Thanks.
There is no drawback in learning Jython -
it is a conformant implementation of Python 2's syntax - and the differences to Python3 are just the one you will find documented everywhere.
I don't know where jython stands in terms of implementation of Python's stdlib - but I believe it has most of Python's 2.7 stdlib in place and working - some modules won't work, like "ctypes" for example. But as far as the language constructs go, you will be fine.
(IMO it is a good tool, not only for what you want, but a nice tool for exploring Java's libraries themselves in an interactive way, since you can use any Java class from the jython interactive shell)
As for the comments talking about unavailable modules: those are 3rd party modules installable on CPython. You certainly don't need them to get the language constructs, like you want. It is a trade off: you loose a lot of the Python ecosystem, but you can use the Java ecosystem in its place. And certainly, when starting a new project, you can just use normal CPython with whatever modules you need: the language is the same.
I am learning Python. My intentions are:
to write a webapp in Python/Django
create an android app (using Jython)
write some python scripts for unix box
I was under (incorrect) impression that because Python has been implemented in Java (Jython) and .NET (IronPython), I could simply write my Python code and run it through either interpreter/compiler.
I thought if I wrote a hello world in CPython and compiled it with Jython, I'd get Java bytecode. If I compliled it with IronPython, I'd get .NET bytecode.
But now it seems like regular Python code won't work with Jython compiler/interpreter. You've to import some fancy Java specific modules. So, that means, I would have to re-write my program for Java using Java modules/libraries.
Any tips on how to write my Python code so that it works everywhere? Web, Unix, Android.
NOTE: I don't want to have to learn Java.
Thanks
print 'Hello, World!'
This works just fine on any Python implementation worthy of the name. So will most other pure-Python code. Where it gets tricky is when using libraries, as Jython and IronPython are missing some standard library modules and don't support C extensions. Dealing with platform-specific code can also present some issues.
If you want your code to be portable, you need to remove as many dependencies as possible from the shared code. The standard library is generally OK (but not complete in either), and pure-Python external modules are generally OK if they only depend on other pure-Python modules.
If you do need to detect them, I believe the canonical checks are:
if os.name == 'java': # Jython
if sys.platform == 'cli': # IronPython
Neither Jython nor IronPython will produce programs that will run without Jython/IronPython being present. In principle it's possible, and it's even possible to compile a subset of Python to pure bytecode; the former requires linking in the Python engine, and the latter would require restricting what parts of Python you could use.
If someone were to provide this for IronPython I wouldn't turn it down, and I doubt the Jython team would either, but I'm not holding my breath. Either option is a lot of work.
Please be more specific about what you are trying to do. What is your regular Python code ? What does not work with it as you expected ?
According to the Jython FAQ, Jython is an implementation of the Python language. The same Python code should produce the same result on Jython or CPython.
I recently started learning Python. Not yet ventured into coding.
During one of my learning sessions, i came accross the term Jython.
I googled it & got some information.
I would like to know if anyone has implemented any real-world program using Jython.
Most of the time, Jython isn't used directly to write full read-world programs, but a lot of programs actually embed Jython to use it as a scripting language.
The official Jython website gives a list of projects, some written in Jython, others using Jython for scripting:
http://wiki.python.org/jython/JythonUsers
I am writing a full application in Jython at the moment, and would highly recommend it. Having all of the Java libraries at your disposal is very handy, and the Python syntax and language features actually make using some of them easier than it is in Java (I'm mostly talking about Swing here).
Check out the chapter on GUI Applications from the Jython book. It does a lot of comparisons like 'Look at all this Java code, and now look at it reduced to Python code of half the length!'.
The only caveats I've found are:
Jython development tends to run slightly behind Python, which can be annoying if you find a cool way of doing something in Python, only to discover it's not supported in the current Jython version.
Occasionally you might have hiccups with the interface between Python and Java (I have a couple of unsolved problems here and here, although there are always workarounds for this kind of thing).
Distribution is not as simple as it could be, although once you figure out how to do it, it's fairly painless. I recommend following the method here. It essentially consists of:
Exploding jython.jar and adding your own modules into it.
Writing and compiling a small Java class that creates a Python interpreter and loads up your Python modules.
Creating an executable .jar file consisting of the jython.jar modules, your own Python modules, and the Java class.
Jython really shines for dependency injection.
You know those pesky variables you have to give your program, like
file system paths
server names
ports
Jython provides a really nice way of injecting those variables by putting them in a script. It works equally well for injecting java dependencies, as well.
WebSphere and WebLogic use it as their default scripting engine for administrative purposes.
A lot of other Oracle products ship it as part of their "oracle_commons" module (Oracle Universal Installer, Oracle HTTP Server etc). It's mostly version 2.2 being deployed though, which is a bit old and clunky.
There is a list of application that uses jython at http://wiki.python.org/jython/JythonUsers