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Programming Python, 3rd Edition
book

Programming Python, 3rd Edition

by Mark Lutz
August 2006
Intermediate to advanced content levelIntermediate to advanced
1600 pages
51h 46m
English
O'Reilly Media, Inc.
Content preview from Programming Python, 3rd Edition

Wrapping C Environment Calls

Let’s move on to a more useful application of C extension modules. The handcoded C file in Example 22-9 integrates the standard C library’s getenv and putenv shell environment variable calls for use in Python scripts.

Example 22-9. PP3E\Integrate\Extend\CEnviron\cenviron.c

/****************************************************************** * A C extension module for Python, called "cenviron". Wraps the * C library's getenv/putenv routines for use in Python programs. ******************************************************************/ #include <Python.h> #include <stdlib.h> #include <string.h> /***********************/ /* 1) module functions */ /***********************/ static PyObject * /* returns object */ wrap_getenv(PyObject *self, PyObject *args) /* self not used */ { /* args from python */ char *varName, *varValue; PyObject *returnObj = NULL; /* null=exception */ if (PyArg_Parse(args, "s", &varName)) { /* Python -> C */ varValue = getenv(varName); /* call C getenv */ if (varValue != NULL) returnObj = Py_BuildValue("s", varValue); /* C -> Python */ else PyErr_SetString(PyExc_SystemError, "Error calling getenv"); } return returnObj; } static PyObject * wrap_putenv(PyObject *self, PyObject *args) { char *varName, *varValue, *varAssign; PyObject *returnObj = NULL; if (PyArg_Parse(args, "(ss)", &varName, &varValue)) { varAssign = malloc(strlen(varName) + strlen(varValue) + 2); sprintf(varAssign, "%s=%s", varName, varValue); if (putenv(varAssign) == 0) ...
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Publisher Resources

ISBN: 0596009259Supplemental ContentErrata Page