package pythonlib

README.md

pythonlib makes it easier to write wrappers around ocaml functions so that they can be called from python.

Example

This example is taken from the examples directory. The ocaml code defines a function that takes as argument an integer n, performs some computations based on n and return a float value. This function is attached to a newly defined python module named ocaml_module.

open Base

let approx_pi =
  let%map_open.Python_lib n = positional "n" int ~docstring:""
  in
  let sum =
    List.init n ~f:(fun i -> let i = Float.of_int (1 + i) in 1.0 /. (i *. i))
    |> List.reduce_exn ~f:(+.)
  in
  Float.sqrt (sum *. 6.) |> python_of_float

let () =
  if not (Py.is_initialized ())
  then Py.initialize ();
  let mod_ = Py_module.create "ocaml_module" in
  Py_module.set mod_ "approx_pi" approx_pi

This code is compiled to a static library python_ocaml_static.so. The python code then loads this library, starts the ocaml runtime which results in creating the ocaml_module module, and then uses the approx_pi function.

# Load the static library containing the ocaml runtime and functions.
from ctypes import *
ocaml_library = './python_ocaml_static.so'
ocaml = PyDLL(ocaml_library, RTLD_GLOBAL)
argv_t = c_char_p * 2
argv = argv_t(ocaml_library.encode('utf-8'), None)
# Start the ocaml runtime.
ocaml.caml_startup(argv)

# Import the module defined in the ocaml code and run the function.
import ocaml_module
print(ocaml_module.approx_pi(1000))

pythonlib also handles keyword arguments as well as basic types such as int, float, string, list, etc. Further examples can be found in the examples directory.