Advanced F2PY usages¶
Adding self-written functions to F2PY generated modules¶
Self-written Python C/API functions can be defined inside signature files using usercode and pymethoddef statements (they must be used inside the python module block). For example, the following signature file spam.pyf
! -*- f90 -*-
python module spam
usercode '''
static char doc_spam_system[] = "Execute a shell command.";
static PyObject *spam_system(PyObject *self, PyObject *args)
{
char *command;
int sts;
if (!PyArg_ParseTuple(args, "s", &command))
return NULL;
sts = system(command);
return Py_BuildValue("i", sts);
}
'''
pymethoddef '''
{"system", spam_system, METH_VARARGS, doc_spam_system},
'''
end python module spam
wraps the C library function system():
f2py -c spam.pyf
In Python:
>>> import spam
>>> status = spam.system('whoami')
pearu
>> status = spam.system('blah')
sh: line 1: blah: command not found
Modifying the dictionary of a F2PY generated module¶
The following example illustrates how to add an user-defined variables to a F2PY generated extension module. Given the following signature file
! -*- f90 -*-
python module var
usercode '''
int BAR = 5;
'''
interface
usercode '''
PyDict_SetItemString(d,"BAR",PyInt_FromLong(BAR));
'''
end interface
end python module
compile it as f2py -c var.pyf.
Notice that the second usercode statement must be defined inside an interface block and where the module dictionary is available through the variable d (see f2py var.pyf-generated varmodule.c for additional details).
In Python:
>>> import var
>>> var.BAR
5