pybind11：从 c/c++ 获取 arguments 到 python function 的编号

Question

In pybind11, I have a variable of type pybind11::function . Is there any way to determine how many arguments that function takes, in c++? Ie if it comes from def f(a, b) , the answer would be 2. I realize this might get crazy w/r *arks, kwargs, self, etc...

To be clear, this is inside of c++, so I'm looking for c++ code.

Answer 1

Here is how you can use inspect.signature() :

from inspect import signature

import os # I only imported os to demonstrate with one of its functions

print(signature(os.remove)) # Print out the arguments for the remove fumction from the os module

Output:

(path, *, dir_fd=None)

Answer 2

So here's how to do this in pybind11:

#include <pybind11/pybind11.h>
#include <pybind11/embed.h>
pybind11::function callback_; // from somewhere!
pybind11::module inspect_module = pybind11::module::import("inspect");
pybind11::object result = inspect_module.attr("signature")(callback_).attr("parameters");
auto num_params = pybind11::len(result);
// num_params is an int