Merge pull request #91 from realpython/jima-python-bindings

Jima python bindings

Author: jima80525

python-bindings/overview_article/cffi_test.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python3
+import cffi_example
+
+if __name__ == "__main__":
+    # Sample data for our call:
+    x, y = 6, 2.3
+
+    answer = cffi_example.lib.cmult(x, y)
+    print(f"    In Python: int: {x} float {y:.1f} return val {answer:.1f}")

python-bindings/overview_article/cmult.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include "cmult.h"
+
+
+float cmult(int int_param, float float_param) {
+    float return_value = int_param * float_param;
+    printf("    In cmult : int: %d float %.1f returning  %.1f\n", int_param,
+            float_param, return_value);
+    return return_value;
+}
+

python-bindings/overview_article/cmult.h

@@ -0,0 +1 @@
+float cmult(int int_param, float float_param);

python-bindings/overview_article/cppmult.cpp

@@ -0,0 +1,15 @@
+#include <iostream>
+#include <iomanip>
+#include "cppmult.hpp"
+
+
+float cppmult(int int_param, float float_param) {
+    float return_value = int_param * float_param;
+    std::cout << std::setprecision(1) << std::fixed
+	          << "    In cppmul: int: " << int_param
+	          << " float " <<  float_param
+	          << " returning  " << return_value
+	          << std::endl;
+    return return_value;
+}
+

python-bindings/overview_article/cppmult.hpp

@@ -0,0 +1 @@
+float cppmult(int int_param, float float_param);

python-bindings/overview_article/ctypes_test.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python
+""" Simple examples of calling C functions through ctypes module. """
+import ctypes
+import pathlib
+
+
+if __name__ == "__main__":
+    # Load the shared library into c types.
+    libname = pathlib.Path().absolute() / "libcmult.so"
+    c_lib = ctypes.CDLL(libname)
+
+    # Sample data for our call:
+    x, y = 6, 2.3
+
+    # This will not work:
+    # answer = c_lib.cmult(x, y)
+
+    # This produces a bad answer:
+    answer = c_lib.cmult(x, ctypes.c_float(y))
+    print(f"    In Python: int: {x} float {y:.1f} return val {answer:.1f}")
+    print()
+
+    # You need tell ctypes that the function returns a float
+    c_lib.cmult.restype = ctypes.c_float
+    answer = c_lib.cmult(x, ctypes.c_float(y))
+    print(f"    In Python: int: {x} float {y:.1f} return val {answer:.1f}")

python-bindings/overview_article/cython_example.pyx

@@ -0,0 +1,7 @@
+""" Example cython interface definition """
+
+cdef extern from "cppmult.hpp":
+    float cppmult(int int_param, float float_param)
+
+def pymult( int_param, float_param ):
+    return cppmult( int_param, float_param )

python-bindings/overview_article/cython_test.py

@@ -0,0 +1,8 @@
+#!/usr/bin/env python
+import cython_example
+
+# Sample data for our call
+x, y = 6, 2.3
+
+answer = cython_example.pymult(x, y)
+print(f"    In Python: int: {x} float {y:.1f} return val {answer:.1f}")

python-bindings/overview_article/pybind11_test.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python
+import pybind11_example
+
+if __name__ == "__main__":
+    # Sample data for our call:
+    x, y = 6, 2.3
+
+    answer = pybind11_example.cpp_function(x, y)
+    print(f"    In Python: int: {x} float {y:.1f} return val {answer:.1f}")

python-bindings/overview_article/pybind11_wrapper.cpp

@@ -0,0 +1,7 @@
+#include <pybind11/pybind11.h>
+#include <cppmult.hpp>
+
+PYBIND11_MODULE(pybind11_example, m) {
+    m.doc() = "pybind11 example plugin"; // Optional module docstring
+    m.def("cpp_function", &cppmult, "A function which multiplies two numbers");
+}