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

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 "example_module" in
  Py_module.set mod_ "approx_pi" approx_pi

This code is compiled to a static library ocaml.so, together with a small C library defining the PyInit_ocaml function that starts the ocaml runtime and exposes the example module. The python code then imports this library and can use the ocaml functions.

# This requires the ocaml.bc.so file to be copied as ocaml.so in the python path
from ocaml import example_module, toploop

# 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.