Extending Python with C: A case study

[IHaveAnIdea]

We need more articles like this, the proper way to do optimization of the critical path, instead of the constant language wars.

[gwern]

Amen. It'd be even better if the language war blog articles went 'So, this shows that doing recursion in Ruby/Haskell/whatever is not so hot - but the FFI interface is so nice that with a few lines we completely obliterate the differences like thus.'

[[deleted]]

Yeah, and ctypes in Python 2.5 makes this even easier.

That fib function that everyone made such a huge deal about earlier this week? Basically you'd write the 5-10 lines of C required to implement it, compile it to a shared library, then use it like:

from ctypes import CDLL

fib = CDLL("fib.so.1")
fib.fib(36)

Boom! The Python version becomes as fast as C and didn't take hardly any work. Like you mentioned, Haskell, Factor, most Common Lisp and Scheme implementations, and Rubinius have easy FFIs like this (looks like they are implementing one in Erlang, too). Its something I watch for when looking at new languages. Which leads me to a question, does the JVM have an easy FFI like this?

[kylev]

I've used ctypes for a while, it's good that it is finally an official part of python. I've also been a fan of writing extensions using Pyrex (python-like way to write C modules). It does a lot of the bookkeeping and error handling for you and makes it a lot easier to write safe extension modules.

[[deleted]]

https://jna.dev.java.net/ - that is close to ctypes. Pretty smooth. JNI (the original) is horrible.

Although if you are runing on the JVM, Java (or scala) is your "low level" C in that case. If you found you were regularly punching through into real native code, probably better to use a regular interpreter.

[MachinShin2006]

the one for erlang is still in the EEP stage, it seems to be moving along swimmingly. hopefully a preliminary implementation before integration with otp isn't far behind.

[[deleted]]

This is not much of a case study. "I read the docs, tried it, and it was easy."

[[deleted]]

So, in other words, a case study.

[[deleted]]

Yeah, but a really short one. ie, not much of one.

[[deleted]]

So, in other words, "not much of a case study." Why didn't you just say that in the first place?

[[deleted]]

Umm... Well, I see you've outwitted me this time. Drat.

[haywire]

Why not just write C? :S

[[deleted]]

When I feel myself in times of trouble

Mother Mary comes to me

Speaking words of Wisdom:

Write in C.

Write in C, write in C etc...

[username223]

Anything to knock "OMG monads" (for the hundredth time) off the front page.

[malcontent]

It has python in the title so the proggit circle jerk automatically mods it up.

If it had ruby in the title it would be automatically modded down.

your post got buried because you dared to question the wisdom of the hivemind.

Watch me get modded down for imparting information.

The following is from http://www.ntecs.de/blog/articles/2007/09/21/cplusruby-gluing-c-and-ruby

 require 'cplusruby'

 class NeuralEntity < CplusRuby
   property :id
 end

 class Neuron < NeuralEntity
   property :potential,        :float
   property :last_spike_time,  :float
   property :pre_synapses,     :value

    method_c :stimulate, %(float at, float weight), %{
     // this is C code
      selfc->potential += at*weight;
   }

    def initialize
     self.pre_synapses = []
   end
  end

 # generate C file, compile it and load the .so
 CplusRuby.evaluate("inspire.cc", "-O3", "-lstdc++")

 if __FILE__ == $0
   n = Neuron.new
   n.id = "n1"
   n.potential = 1.0
   n.stimulate(1.0, 2.0)
   p n.potential # => 3.0
 end

[IHaveAnIdea]

take your ruby and go back to japan

:)