Build Python binding of C++ library with cffi (PyPy/Py3K compatible)

README.rst

Run with Python:

pip-2.7 install cffi
PYTHON=python2.7 sh go.sh

Run with PyPy:

pip-pypy install cffi
PYTHON=pypy sh go.sh

Run with Py3K:

pip-3.3 install cffi
PYTHON=python3.3 sh go.sh

The expected output:

=> now run the native one
hello, world
=> now run the pypy bound one
hello, cffi

go.sh

#!/usr/bin/env sh

set -e

[ -z "$PYTHON" ] && PYTHON="python"

g++ -o ./hello ./libhello.cpp
echo "=> now run the native one"
./hello

g++ -o ./libhello.so ./libhello.cpp -fPIC -shared
echo "=> now run the $PYTHON bound one"
python hello.py

hello.py

import cffi


ffi = cffi.FFI()
ffi.cdef("void cffi_hello(char *name);")
C = ffi.dlopen("./libhello.so")


def hello(name):
    C.cffi_hello(name)


if __name__ == "__main__":
    hello("cffi")

libhello.cpp

#include <iostream>

class User
{
    std::string name;
    public:
        User(char *name):name(name) {}
        User(std::string &name):name(name) {}

        std::string greet() { return "hello, " + name; }
};

void hello(char *name)
{
    User user(name);
    std::cout << user.greet() << std::endl;
}

int main()
{
    hello((char *) "world");
    return 0;
}

extern "C"
{
    extern void cffi_hello(char *name)
    {
        return hello(name);
    }
}

This is extremely helpful. Thanks!

Thanks! Really useful indeed.

Like it

very helpful. thanks!

Traceback (most recent call last):
File "hello.py", line 12, in
hello("cffi")
File "hello.py", line 8, in hello
C.cffi_hello(name)
TypeError: initializer for ctype 'char *' must be a bytes or list or tuple, not str

I am getting this error.... can't find why

Just found a solution to use hello("cffi".encode("ascii"))

Just found a solution to use hello("cffi".encode("ascii"))

You are right. The str and bytes are significantly different things in Python 3.

This works too:

hello(b"explicit bytes")

Thanks, this is nice. Could you also post an example for Windows with MSVC? Thanks.