Initial commit

Author: fpoli

.gitignore

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+*~
+
+*.o
+*.so
+
+__pycache__/
+*.pyc
+*.pyo

Makefile

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+# Declaration of variables
+CC = gcc
+CC_FLAGS = -shared -fPIC -I/usr/include/python2.7 \
+	-Wall -Wextra -Wno-unused-parameter -O2 -g
+
+# File names
+SOURCES = $(wildcard *.c)
+OBJECTS = $(SOURCES:module.c=.so)
+
+# Main target
+all: $(OBJECTS)
+
+# Object files
+%.so: %module.c
+	$(CC) $(CC_FLAGS) $< -o $@
+
+run: $(OBJECTS)
+	python -c "import fib; print fib.fib(5)"
+	python -c "import hello; hello.greet('Foobar')"
+
+# To remove generated files
+clean:
+	rm -f *.so
+
+.PHONY: all run clean

Readme.md

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+Python/C API quick start
+=========================
+
+A quick example of Python 2.7 modules implemented in C using the Python/C API.
+
+```
+make all
+python -c "import hello; hello.say_hello('World')"
+python -c "import fib; print fib.fib(5)"
+make clean
+```
+
+Note that the best way to distribute a Python module is to use a `setup.py`
+file. The Makefile is here only to debunk Python's magic.
+
+
+## Steps
+
+1. Write a `foobarmodule.c` C file.
+   Note the `#include <Python.h>` at the beginning of example files.
+2. Compile `foobarmodule.c` and produce a `foobar.so` file.
+   See the Makefile for details.
+3. Put `foobar.so` in a folder listed in the Python path.
+4. Load the module from Python with `import foobar`.

equivalent_fib.py

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+
+def fib(n):
+    "Calculate the Fibonacci numbers (in Python)."
+    if n <= 1:
+        return n
+    else
+        return fib(n-1) + fib(n-2)

equivalent_hello.py

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+
+def greet(name):
+    "Greet somebody (in Python)."
+    print "Hello", name

fibmodule.c

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+#include <Python.h>
+
+int _fib(int n)
+{
+    printf("Debug: calling _fib(%d)\n", n);
+    if (n <= 1)
+        return n;
+    else
+        return _fib(n-1) + _fib(n-2);
+}
+
+/* Wrapped _fib function */
+static PyObject* fib(PyObject* self, PyObject* args)
+{
+    int n;
+
+    /* Parse the input, from Python integer to C int */
+    if (!PyArg_ParseTuple(args, "i", &n))
+        return NULL;
+    /* If the above function returns -1, an appropriate Python exception will
+     * have been set, and the function simply returns NULL
+     */
+
+    /* Construct the result: a Python integer object */
+    return Py_BuildValue("i", _fib(n));
+}
+
+/* Define functions in module */
+static PyMethodDef FibMethods[] = {
+    {"fib", fib, METH_VARARGS, "Calculate the Fibonacci numbers (in C)."},
+    {NULL, NULL, 0, NULL}  /* Sentinel */
+};
+
+/* Module initialization */
+PyMODINIT_FUNC
+initfib(void)
+{
+    (void) Py_InitModule("fib", FibMethods);
+}

hellomodule.c

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+#include <Python.h>
+
+static PyObject* greet(PyObject* self, PyObject* args)
+{
+    const char* name;
+
+    /* Parse the input, from Python string to C string */
+    if (!PyArg_ParseTuple(args, "s", &name))
+        return NULL;
+    /* If the above function returns -1, an appropriate Python exception will
+     * have been set, and the function simply returns NULL
+     */
+
+    printf("Hello %s\n", name);
+
+    /* Returns a None Python object */
+    Py_RETURN_NONE;
+}
+
+/* Define functions in module */
+static PyMethodDef HelloMethods[] = {
+    {"greet", greet, METH_VARARGS, "Greet somebody (in C)."},
+    {NULL, NULL, 0, NULL}  /* Sentinel */
+};
+
+/* Module initialization */
+PyMODINIT_FUNC
+inithello(void)
+{
+    (void) Py_InitModule("hello", HelloMethods);
+}