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paulrosspaulross
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Initial stab at an object using sequence methods.
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‎doc/sphinx/source/new_types.rst‎

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@@ -393,6 +393,35 @@ This can be tested thus, in ``tests/unit/test_c_object.py``:
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obj.some_attr
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assert err.value.args[0] == "'cObject.ObjectWithAttributes' object has no attribute 'some_attr'"
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.. _sq_length: https://docs.python.org/3/c-api/typeobj.html#c.PySequenceMethods.sq_length
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.. _lenfunc: https://docs.python.org/3/c-api/typeobj.html#c.lenfunc
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---------------
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Sequence Types
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---------------
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.. todo::
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"Creating New Types": Add a section on making an object act like a sequence using
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`tp_as_sequence <https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_as_sequence>`_.
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See also `Sequence Object Structures <https://docs.python.org/3/c-api/typeobj.html#sequence-structs>`_
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.. list-table:: Sequence Methods
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:widths: 20 70 10
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:header-rows: 1
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* - Member
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- Function Type
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- Function Signatures
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- Description
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* - `sq_length`_
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- `lenfunc`_
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- ``typedef Py_ssize_t (*lenfunc)(PyObject*)``
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- Returns the length of the sequence.
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---------------
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TODOs:
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---------------
@@ -403,12 +432,6 @@ TODOs:
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`tp_as_number <https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_as_number>`_.
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See also `Number Object Structures <https://docs.python.org/3/c-api/typeobj.html#number-structs>`_
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.. todo::
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"Creating New Types": Add a section on making an object act like a sequence using
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`tp_as_sequence <https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_as_sequence>`_.
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See also `Sequence Object Structures <https://docs.python.org/3/c-api/typeobj.html#sequence-structs>`_
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.. todo::
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"Creating New Types": Add a section on making an object act like a mapping object (like a ``dict``) using

‎src/cpy/Object/cSeqObject.c‎

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@@ -0,0 +1,194 @@
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//
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// Created by Paul Ross on 08/07/2021.
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//
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// Example of an object implementing the sequence methods with PySequenceMethods.
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//
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// See also src/cpy/Iterators/cIterator.c
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#define PY_SSIZE_T_CLEAN
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#include <Python.h>
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#include "structmember.h"
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typedef struct {
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PyObject_HEAD
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long *array_long;
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ssize_t size;
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} SequenceOfLong;
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// Forward reference
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static int is_sequence_of_long_type(PyObject *op);
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static PyObject *
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SequenceOfLong_new(PyTypeObject *type, PyObject *Py_UNUSED(args), PyObject *Py_UNUSED(kwds)) {
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SequenceOfLong *self;
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self = (SequenceOfLong *) type->tp_alloc(type, 0);
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if (self != NULL) {
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assert(!PyErr_Occurred());
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self->size = 0;
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self->array_long = NULL;
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}
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return (PyObject *) self;
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}
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static int
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SequenceOfLong_init(SequenceOfLong *self, PyObject *args, PyObject *kwds) {
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static char *kwlist[] = {"sequence", NULL};
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PyObject *sequence = NULL;
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if (!PyArg_ParseTupleAndKeywords(args, kwds, "O", kwlist, &sequence)) {
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return -1;
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}
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if (!PySequence_Check(sequence)) {
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return -2;
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}
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self->size = PySequence_Length(sequence);
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self->array_long = malloc(self->size * sizeof(long));
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if (!self->array_long) {
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return -3;
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}
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for (Py_ssize_t i = 0; i < PySequence_Length(sequence); ++i) {
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// New reference.
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PyObject *py_value = PySequence_GetItem(sequence, i);
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if (PyLong_Check(py_value)) {
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self->array_long[i] = PyLong_AsLong(py_value);
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Py_DECREF(py_value);
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} else {
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PyErr_Format(
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PyExc_TypeError,
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"Argument [%zd] must be a int, not type %s",
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i,
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Py_TYPE(sequence)->tp_name
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);
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// Clean up on error.
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free(self->array_long);
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self->array_long = NULL;
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Py_DECREF(py_value);
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return -4;
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}
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}
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return 0;
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}
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static void
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SequenceOfLong_dealloc(SequenceOfLong *self) {
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free(self->array_long);
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Py_TYPE(self)->tp_free((PyObject *) self);
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}
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//static PyObject *
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//SequenceOfLong_size(SequenceOfLong *self, PyObject *Py_UNUSED(ignored)) {
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// return Py_BuildValue("n", self->size);
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//}
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static PyMethodDef SequenceOfLong_methods[] = {
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// {
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// "size",
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// (PyCFunction) SequenceOfLong_size,
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// METH_NOARGS,
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// "Return the size of the sequence."
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// },
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{NULL, NULL, 0, NULL} /* Sentinel */
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};
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/* Sequence methods. */
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static Py_ssize_t
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SequenceOfLong_len(PyObject *self) {
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return ((SequenceOfLong *)self)->size;
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}
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static PyObject *
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SequenceOfLong_getitem(PyObject *self, Py_ssize_t index) {
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Py_ssize_t my_index = index;
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if (my_index < 0) {
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my_index += SequenceOfLong_len(self);
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}
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if (my_index > SequenceOfLong_len(self)) {
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PyErr_Format(
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PyExc_IndexError,
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"Index %ld is out of range for length %ld",
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index,
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SequenceOfLong_len(self)
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);
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return NULL;
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}
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return PyLong_FromLong(((SequenceOfLong *)self)->array_long[my_index]);
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}
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PySequenceMethods SequenceOfLong_sequence_methods = {
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.sq_length = &SequenceOfLong_len,
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.sq_concat = NULL,
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.sq_repeat = NULL,
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.sq_item = &SequenceOfLong_getitem,
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.sq_ass_item = NULL,
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.sq_contains = NULL,
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.sq_inplace_concat = NULL,
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.sq_inplace_repeat = NULL,
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};
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static PyObject *
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SequenceOfLong___str__(SequenceOfLong *self, PyObject *Py_UNUSED(ignored)) {
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assert(!PyErr_Occurred());
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return PyUnicode_FromFormat("<SequenceOfLong sequence size: %ld>", self->size);
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}
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static PyTypeObject SequenceOfLongType = {
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PyVarObject_HEAD_INIT(NULL, 0)
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.tp_name = "SequenceOfLong",
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.tp_basicsize = sizeof(SequenceOfLong),
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.tp_itemsize = 0,
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.tp_dealloc = (destructor) SequenceOfLong_dealloc,
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.tp_as_sequence = &SequenceOfLong_sequence_methods,
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.tp_str = (reprfunc) SequenceOfLong___str__,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
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.tp_doc = "Sequence of long integers.",
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.tp_methods = SequenceOfLong_methods,
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.tp_init = (initproc) SequenceOfLong_init,
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.tp_new = SequenceOfLong_new,
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};
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static int
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is_sequence_of_long_type(PyObject *op) {
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return Py_TYPE(op) == &SequenceOfLongType;
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}
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static PyMethodDef cIterator_methods[] = {
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// {"iterate_and_print", (PyCFunction) iterate_and_print, METH_VARARGS,
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// "Iteratee through the argument printing the values."},
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{NULL, NULL, 0, NULL} /* Sentinel */
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};
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static PyModuleDef sequence_object_cmodule = {
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PyModuleDef_HEAD_INIT,
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.m_name = "cSeqObject",
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.m_doc = (
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"Example module that creates an extension type with sequence methods"
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),
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.m_size = -1,
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.m_methods = cIterator_methods,
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};
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PyMODINIT_FUNC
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PyInit_cSeqObject(void) {
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PyObject *m;
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m = PyModule_Create(&sequence_object_cmodule);
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if (m == NULL) {
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return NULL;
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}
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if (PyType_Ready(&SequenceOfLongType) < 0) {
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Py_DECREF(m);
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return NULL;
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}
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Py_INCREF(&SequenceOfLongType);
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if (PyModule_AddObject(
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m,
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"SequenceOfLong",
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(PyObject *) &SequenceOfLongType) < 0
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) {
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Py_DECREF(&SequenceOfLongType);
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Py_DECREF(m);
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return NULL;
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}
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return m;
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}

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