# SOME DESCRIPTIVE TITLE.

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# This file is distributed under the same license as the Python package.

# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.

#

# Translators:

# python-doc bot, 2025

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msgid ""

msgstr ""

"Project-Id-Version: Python 3.14\n"

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"PO-Revision-Date: 2025-09-16 00:00+0000\n"

"Last-Translator: python-doc bot, 2025\n"

"Language-Team: German (https://app.transifex.com/python-doc/teams/5390/de/)\n"

"Language: de\n"

"MIME-Version: 1.0\n"

"Content-Type: text/plain; charset=UTF-8\n"

"Content-Transfer-Encoding: 8bit\n"

"Plural-Forms: nplurals=2; plural=(n != 1);\n"

#: ../../extending/newtypes_tutorial.rst:7

msgid "Defining Extension Types: Tutorial"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:14

msgid ""

"Python allows the writer of a C extension module to define new types that "

"can be manipulated from Python code, much like the built-in :class:`str` "

"and :class:`list` types. The code for all extension types follows a "

"pattern, but there are some details that you need to understand before you "

"can get started. This document is a gentle introduction to the topic."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:24

msgid "The Basics"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:26

msgid ""

"The :term:`CPython` runtime sees all Python objects as variables of type :c:"

"expr:`PyObject*`, which serves as a \"base type\" for all Python objects. "

"The :c:type:`PyObject` structure itself only contains the object's :term:"

"`reference count` and a pointer to the object's \"type object\". This is "

"where the action is; the type object determines which (C) functions get "

"called by the interpreter when, for instance, an attribute gets looked up on "

"an object, a method called, or it is multiplied by another object. These C "

"functions are called \"type methods\"."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:35

msgid ""

"So, if you want to define a new extension type, you need to create a new "

"type object."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:38

msgid ""

"This sort of thing can only be explained by example, so here's a minimal, "

"but complete, module that defines a new type named :class:`!Custom` inside a "

"C extension module :mod:`!custom`:"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:43

msgid ""

"What we're showing here is the traditional way of defining *static* "

"extension types. It should be adequate for most uses. The C API also "

"allows defining heap-allocated extension types using the :c:func:"

"`PyType_FromSpec` function, which isn't covered in this tutorial."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:48

msgid ""

"#define PY_SSIZE_T_CLEAN\n"

"#include <Python.h>\n"

"\n"

"typedef struct {\n"

" PyObject_HEAD\n"

" /* Type-specific fields go here. */\n"

"} CustomObject;\n"

"\n"

"static PyTypeObject CustomType = {\n"

" .ob_base = PyVarObject_HEAD_INIT(NULL, 0)\n"

" .tp_name = \"custom.Custom\",\n"

" .tp_doc = PyDoc_STR(\"Custom objects\"),\n"

" .tp_basicsize = sizeof(CustomObject),\n"

" .tp_itemsize = 0,\n"

" .tp_flags = Py_TPFLAGS_DEFAULT,\n"

" .tp_new = PyType_GenericNew,\n"

"};\n"

"\n"

"static int\n"

"custom_module_exec(PyObject *m)\n"

"{\n"

" if (PyType_Ready(&CustomType) < 0) {\n"

" return -1;\n"

" }\n"

"\n"

" if (PyModule_AddObjectRef(m, \"Custom\", (PyObject *) &CustomType) < 0) "

"{\n"

" return -1;\n"

" }\n"

"\n"

" return 0;\n"

"}\n"

"\n"

"static PyModuleDef_Slot custom_module_slots[] = {\n"

" {Py_mod_exec, custom_module_exec},\n"

" // Just use this while using static types\n"

" {Py_mod_multiple_interpreters, "

"Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},\n"

" {0, NULL}\n"

"};\n"

"\n"

"static PyModuleDef custom_module = {\n"

" .m_base = PyModuleDef_HEAD_INIT,\n"

" .m_name = \"custom\",\n"

" .m_doc = \"Example module that creates an extension type.\",\n"

" .m_size = 0,\n"

" .m_slots = custom_module_slots,\n"

"};\n"

"\n"

"PyMODINIT_FUNC\n"

"PyInit_custom(void)\n"

"{\n"

" return PyModuleDef_Init(&custom_module);\n"

"}\n"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:50

msgid ""

"Now that's quite a bit to take in at once, but hopefully bits will seem "

"familiar from the previous chapter. This file defines three things:"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:53

msgid ""

"What a :class:`!Custom` **object** contains: this is the ``CustomObject`` "

"struct, which is allocated once for each :class:`!Custom` instance."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:55

msgid ""

"How the :class:`!Custom` **type** behaves: this is the ``CustomType`` "

"struct, which defines a set of flags and function pointers that the "

"interpreter inspects when specific operations are requested."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:58

msgid ""

"How to define and execute the :mod:`!custom` module: this is the "

"``PyInit_custom`` function and the associated ``custom_module`` struct for "

"defining the module, and the ``custom_module_exec`` function to set up a "

"fresh module object."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:63

msgid "The first bit is::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:65

msgid ""

"typedef struct {\n"

" PyObject_HEAD\n"

"} CustomObject;"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:69

msgid ""

"This is what a Custom object will contain. ``PyObject_HEAD`` is mandatory "

"at the start of each object struct and defines a field called ``ob_base`` of "

"type :c:type:`PyObject`, containing a pointer to a type object and a "

"reference count (these can be accessed using the macros :c:macro:`Py_TYPE` "

"and :c:macro:`Py_REFCNT` respectively). The reason for the macro is to "

"abstract away the layout and to enable additional fields in :ref:`debug "

"builds <debug-build>`."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:78

msgid ""

"There is no semicolon above after the :c:macro:`PyObject_HEAD` macro. Be "

"wary of adding one by accident: some compilers will complain."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:81

msgid ""

"Of course, objects generally store additional data besides the standard "

"``PyObject_HEAD`` boilerplate; for example, here is the definition for "

"standard Python floats::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:85

msgid ""

"typedef struct {\n"

" PyObject_HEAD\n"

" double ob_fval;\n"

"} PyFloatObject;"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:90

msgid "The second bit is the definition of the type object. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:92

msgid ""

"static PyTypeObject CustomType = {\n"

" .ob_base = PyVarObject_HEAD_INIT(NULL, 0)\n"

" .tp_name = \"custom.Custom\",\n"

" .tp_doc = PyDoc_STR(\"Custom objects\"),\n"

" .tp_basicsize = sizeof(CustomObject),\n"

" .tp_itemsize = 0,\n"

" .tp_flags = Py_TPFLAGS_DEFAULT,\n"

" .tp_new = PyType_GenericNew,\n"

"};"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:103

msgid ""

"We recommend using C99-style designated initializers as above, to avoid "

"listing all the :c:type:`PyTypeObject` fields that you don't care about and "

"also to avoid caring about the fields' declaration order."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:107

msgid ""

"The actual definition of :c:type:`PyTypeObject` in :file:`object.h` has many "

"more :ref:`fields <type-structs>` than the definition above. The remaining "

"fields will be filled with zeros by the C compiler, and it's common practice "

"to not specify them explicitly unless you need them."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:112

msgid "We're going to pick it apart, one field at a time::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:114

msgid ".ob_base = PyVarObject_HEAD_INIT(NULL, 0)"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:116

msgid ""

"This line is mandatory boilerplate to initialize the ``ob_base`` field "

"mentioned above. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:119

msgid ".tp_name = \"custom.Custom\","

msgstr ""

#: ../../extending/newtypes_tutorial.rst:121

msgid ""

"The name of our type. This will appear in the default textual "

"representation of our objects and in some error messages, for example:"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:124

msgid ""

">>> \"\" + custom.Custom()\n"

"Traceback (most recent call last):\n"

" File \"<stdin>\", line 1, in <module>\n"

"TypeError: can only concatenate str (not \"custom.Custom\") to str"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:131

msgid ""

"Note that the name is a dotted name that includes both the module name and "

"the name of the type within the module. The module in this case is :mod:`!"

"custom` and the type is :class:`!Custom`, so we set the type name to :class:"

"`!custom.Custom`. Using the real dotted import path is important to make "

"your type compatible with the :mod:`pydoc` and :mod:`pickle` modules. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:137

msgid ""

".tp_basicsize = sizeof(CustomObject),\n"

".tp_itemsize = 0,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:140

msgid ""

"This is so that Python knows how much memory to allocate when creating new :"

"class:`!Custom` instances. :c:member:`~PyTypeObject.tp_itemsize` is only "

"used for variable-sized objects and should otherwise be zero."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:146

msgid ""

"If you want your type to be subclassable from Python, and your type has the "

"same :c:member:`~PyTypeObject.tp_basicsize` as its base type, you may have "

"problems with multiple inheritance. A Python subclass of your type will "

"have to list your type first in its :attr:`~type.__bases__`, or else it will "

"not be able to call your type's :meth:`~object.__new__` method without "

"getting an error. You can avoid this problem by ensuring that your type has "

"a larger value for :c:member:`~PyTypeObject.tp_basicsize` than its base type "

"does. Most of the time, this will be true anyway, because either your base "

"type will be :class:`object`, or else you will be adding data members to "

"your base type, and therefore increasing its size."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:156

msgid "We set the class flags to :c:macro:`Py_TPFLAGS_DEFAULT`. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:158

msgid ".tp_flags = Py_TPFLAGS_DEFAULT,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:160

msgid ""

"All types should include this constant in their flags. It enables all of "

"the members defined until at least Python 3.3. If you need further members, "

"you will need to OR the corresponding flags."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:164

msgid ""

"We provide a doc string for the type in :c:member:`~PyTypeObject.tp_doc`. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:166

msgid ".tp_doc = PyDoc_STR(\"Custom objects\"),"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:168

msgid ""

"To enable object creation, we have to provide a :c:member:`~PyTypeObject."

"tp_new` handler. This is the equivalent of the Python method :meth:`~object."

"__new__`, but has to be specified explicitly. In this case, we can just use "

"the default implementation provided by the API function :c:func:"

"`PyType_GenericNew`. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:173

msgid ".tp_new = PyType_GenericNew,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:175

msgid ""

"Everything else in the file should be familiar, except for some code in :c:"

"func:`!custom_module_exec`::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:178

msgid ""

"if (PyType_Ready(&CustomType) < 0) {\n"

" return -1;\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:182

msgid ""

"This initializes the :class:`!Custom` type, filling in a number of members "

"to the appropriate default values, including :c:member:`~PyObject.ob_type` "

"that we initially set to ``NULL``. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:186

msgid ""

"if (PyModule_AddObjectRef(m, \"Custom\", (PyObject *) &CustomType) < 0) {\n"

" return -1;\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:190

msgid ""

"This adds the type to the module dictionary. This allows us to create :"

"class:`!Custom` instances by calling the :class:`!Custom` class:"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:193

msgid ""

">>> import custom\n"

">>> mycustom = custom.Custom()"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:198

msgid ""

"That's it! All that remains is to build it; put the above code in a file "

"called :file:`custom.c`,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:201

msgid ""

"[build-system]\n"

"requires = [\"setuptools\"]\n"

"build-backend = \"setuptools.build_meta\"\n"

"\n"

"[project]\n"

"name = \"custom\"\n"

"version = \"1\"\n"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:203

msgid "in a file called :file:`pyproject.toml`, and"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:205

msgid ""

"from setuptools import Extension, setup\n"

"setup(ext_modules=[Extension(\"custom\", [\"custom.c\"])])"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:210

msgid "in a file called :file:`setup.py`; then typing"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:212

#: ../../extending/newtypes_tutorial.rst:550

msgid "$ python -m pip install ."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:216

msgid ""

"in a shell should produce a file :file:`custom.so` in a subdirectory and "

"install it; now fire up Python --- you should be able to ``import custom`` "

"and play around with ``Custom`` objects."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:220

msgid "That wasn't so hard, was it?"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:222

msgid ""

"Of course, the current Custom type is pretty uninteresting. It has no data "

"and doesn't do anything. It can't even be subclassed."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:227

msgid "Adding data and methods to the Basic example"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:229

msgid ""

"Let's extend the basic example to add some data and methods. Let's also "

"make the type usable as a base class. We'll create a new module, :mod:`!"

"custom2` that adds these capabilities:"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:233

msgid ""

"#define PY_SSIZE_T_CLEAN\n"

"#include <Python.h>\n"

"#include <stddef.h> /* for offsetof() */\n"

"\n"

"typedef struct {\n"

" PyObject_HEAD\n"

" PyObject *first; /* first name */\n"

" PyObject *last; /* last name */\n"

" int number;\n"

"} CustomObject;\n"

"\n"

"static void\n"

"Custom_dealloc(PyObject *op)\n"

"{\n"

" CustomObject *self = (CustomObject *) op;\n"

" Py_XDECREF(self->first);\n"

" Py_XDECREF(self->last);\n"

" Py_TYPE(self)->tp_free(self);\n"

"}\n"

"\n"

"static PyObject *\n"

"Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)\n"

"{\n"

" CustomObject *self;\n"

" self = (CustomObject *) type->tp_alloc(type, 0);\n"

" if (self != NULL) {\n"

" self->first = Py_GetConstant(Py_CONSTANT_EMPTY_STR);\n"

" if (self->first == NULL) {\n"

" Py_DECREF(self);\n"

" return NULL;\n"

" }\n"

" self->last = Py_GetConstant(Py_CONSTANT_EMPTY_STR);\n"

" if (self->last == NULL) {\n"

" Py_DECREF(self);\n"

" return NULL;\n"

" }\n"

" self->number = 0;\n"

" }\n"

" return (PyObject *) self;\n"

"}\n"

"\n"

"static int\n"

"Custom_init(PyObject *op, PyObject *args, PyObject *kwds)\n"

"{\n"

" CustomObject *self = (CustomObject *) op;\n"

" static char *kwlist[] = {\"first\", \"last\", \"number\", NULL};\n"

" PyObject *first = NULL, *last = NULL;\n"

"\n"

" if (!PyArg_ParseTupleAndKeywords(args, kwds, \"|OOi\", kwlist,\n"

" &first, &last,\n"

" &self->number))\n"

" return -1;\n"

"\n"

" if (first) {\n"

" Py_XSETREF(self->first, Py_NewRef(first));\n"

" }\n"

" if (last) {\n"

" Py_XSETREF(self->last, Py_NewRef(last));\n"

" }\n"

" return 0;\n"

"}\n"

"\n"

"static PyMemberDef Custom_members[] = {\n"

" {\"first\", Py_T_OBJECT_EX, offsetof(CustomObject, first), 0,\n"

" \"first name\"},\n"

" {\"last\", Py_T_OBJECT_EX, offsetof(CustomObject, last), 0,\n"

" \"last name\"},\n"

" {\"number\", Py_T_INT, offsetof(CustomObject, number), 0,\n"

" \"custom number\"},\n"

" {NULL} /* Sentinel */\n"

"};\n"

"\n"

"static PyObject *\n"

"Custom_name(PyObject *op, PyObject *Py_UNUSED(dummy))\n"

"{\n"

" CustomObject *self = (CustomObject *) op;\n"

" if (self->first == NULL) {\n"

" PyErr_SetString(PyExc_AttributeError, \"first\");\n"

" return NULL;\n"

" }\n"

" if (self->last == NULL) {\n"

" PyErr_SetString(PyExc_AttributeError, \"last\");\n"

" return NULL;\n"

" }\n"

" return PyUnicode_FromFormat(\"%S %S\", self->first, self->last);\n"

"}\n"

"\n"

"static PyMethodDef Custom_methods[] = {\n"

" {\"name\", Custom_name, METH_NOARGS,\n"

" \"Return the name, combining the first and last name\"\n"

" },\n"

" {NULL} /* Sentinel */\n"

"};\n"

"\n"

"static PyTypeObject CustomType = {\n"

" .ob_base = PyVarObject_HEAD_INIT(NULL, 0)\n"

" .tp_name = \"custom2.Custom\",\n"

" .tp_doc = PyDoc_STR(\"Custom objects\"),\n"

" .tp_basicsize = sizeof(CustomObject),\n"

" .tp_itemsize = 0,\n"

" .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,\n"

" .tp_new = Custom_new,\n"

" .tp_init = Custom_init,\n"

" .tp_dealloc = Custom_dealloc,\n"

" .tp_members = Custom_members,\n"

" .tp_methods = Custom_methods,\n"

"};\n"

"\n"

"static int\n"

"custom_module_exec(PyObject *m)\n"

"{\n"

" if (PyType_Ready(&CustomType) < 0) {\n"

" return -1;\n"

" }\n"

"\n"

" if (PyModule_AddObjectRef(m, \"Custom\", (PyObject *) &CustomType) < 0) "

"{\n"

" return -1;\n"

" }\n"

"\n"

" return 0;\n"

"}\n"

"\n"

"static PyModuleDef_Slot custom_module_slots[] = {\n"

" {Py_mod_exec, custom_module_exec},\n"

" {Py_mod_multiple_interpreters, "

"Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},\n"

" {0, NULL}\n"

"};\n"

"\n"

"static PyModuleDef custom_module = {\n"

" .m_base = PyModuleDef_HEAD_INIT,\n"

" .m_name = \"custom2\",\n"

" .m_doc = \"Example module that creates an extension type.\",\n"

" .m_size = 0,\n"

" .m_slots = custom_module_slots,\n"

"};\n"

"\n"

"PyMODINIT_FUNC\n"

"PyInit_custom2(void)\n"

"{\n"

" return PyModuleDef_Init(&custom_module);\n"

"}\n"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:236

msgid "This version of the module has a number of changes."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:238

msgid ""

"The :class:`!Custom` type now has three data attributes in its C struct, "

"*first*, *last*, and *number*. The *first* and *last* variables are Python "

"strings containing first and last names. The *number* attribute is a C "

"integer."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:242

msgid "The object structure is updated accordingly::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:244

msgid ""

"typedef struct {\n"

" PyObject_HEAD\n"

" PyObject *first; /* first name */\n"

" PyObject *last; /* last name */\n"

" int number;\n"

"} CustomObject;"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:251

msgid ""

"Because we now have data to manage, we have to be more careful about object "

"allocation and deallocation. At a minimum, we need a deallocation method::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:254

msgid ""

"static void\n"

"Custom_dealloc(PyObject *op)\n"

"{\n"

" CustomObject *self = (CustomObject *) op;\n"

" Py_XDECREF(self->first);\n"

" Py_XDECREF(self->last);\n"

" Py_TYPE(self)->tp_free(self);\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:263

msgid "which is assigned to the :c:member:`~PyTypeObject.tp_dealloc` member::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:265

msgid ".tp_dealloc = Custom_dealloc,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:267

msgid ""

"This method first clears the reference counts of the two Python attributes. :"

"c:func:`Py_XDECREF` correctly handles the case where its argument is "

"``NULL`` (which might happen here if ``tp_new`` failed midway). It then "

"calls the :c:member:`~PyTypeObject.tp_free` member of the object's type "

"(computed by ``Py_TYPE(self)``) to free the object's memory. Note that the "

"object's type might not be :class:`!CustomType`, because the object may be "

"an instance of a subclass."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:277

msgid ""

"The explicit cast to ``CustomObject *`` above is needed because we defined "

"``Custom_dealloc`` to take a ``PyObject *`` argument, as the ``tp_dealloc`` "

"function pointer expects to receive a ``PyObject *`` argument. By assigning "

"to the ``tp_dealloc`` slot of a type, we declare that it can only be called "

"with instances of our ``CustomObject`` class, so the cast to ``(CustomObject "

"*)`` is safe. This is object-oriented polymorphism, in C!"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:285

msgid ""

"In existing code, or in previous versions of this tutorial, you might see "

"similar functions take a pointer to the subtype object structure "

"(``CustomObject*``) directly, like this::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:289

msgid ""

"Custom_dealloc(CustomObject *self)\n"

"{\n"

" Py_XDECREF(self->first);\n"

" Py_XDECREF(self->last);\n"

" Py_TYPE(self)->tp_free((PyObject *) self);\n"

"}\n"

"...\n"

".tp_dealloc = (destructor) Custom_dealloc,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:298

msgid ""

"This does the same thing on all architectures that CPython supports, but "

"according to the C standard, it invokes undefined behavior."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:302

msgid ""

"We want to make sure that the first and last names are initialized to empty "

"strings, so we provide a ``tp_new`` implementation::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:305

msgid ""

"static PyObject *\n"

"Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)\n"

"{\n"

" CustomObject *self;\n"

" self = (CustomObject *) type->tp_alloc(type, 0);\n"

" if (self != NULL) {\n"

" self->first = PyUnicode_FromString(\"\");\n"

" if (self->first == NULL) {\n"

" Py_DECREF(self);\n"

" return NULL;\n"

" }\n"

" self->last = PyUnicode_FromString(\"\");\n"

" if (self->last == NULL) {\n"

" Py_DECREF(self);\n"

" return NULL;\n"

" }\n"

" self->number = 0;\n"

" }\n"

" return (PyObject *) self;\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:326

msgid "and install it in the :c:member:`~PyTypeObject.tp_new` member::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:328

msgid ".tp_new = Custom_new,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:330

msgid ""

"The ``tp_new`` handler is responsible for creating (as opposed to "

"initializing) objects of the type. It is exposed in Python as the :meth:"

"`~object.__new__` method. It is not required to define a ``tp_new`` member, "

"and indeed many extension types will simply reuse :c:func:"

"`PyType_GenericNew` as done in the first version of the :class:`!Custom` "

"type above. In this case, we use the ``tp_new`` handler to initialize the "

"``first`` and ``last`` attributes to non-``NULL`` default values."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:338

msgid ""

"``tp_new`` is passed the type being instantiated (not necessarily "

"``CustomType``, if a subclass is instantiated) and any arguments passed when "

"the type was called, and is expected to return the instance created. "

"``tp_new`` handlers always accept positional and keyword arguments, but they "

"often ignore the arguments, leaving the argument handling to initializer (a."

"k.a. ``tp_init`` in C or ``__init__`` in Python) methods."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:346

msgid ""

"``tp_new`` shouldn't call ``tp_init`` explicitly, as the interpreter will do "

"it itself."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:349

msgid ""

"The ``tp_new`` implementation calls the :c:member:`~PyTypeObject.tp_alloc` "

"slot to allocate memory::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:352

msgid "self = (CustomObject *) type->tp_alloc(type, 0);"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:354

msgid ""

"Since memory allocation may fail, we must check the :c:member:`~PyTypeObject."

"tp_alloc` result against ``NULL`` before proceeding."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:358

msgid ""

"We didn't fill the :c:member:`~PyTypeObject.tp_alloc` slot ourselves. "

"Rather :c:func:`PyType_Ready` fills it for us by inheriting it from our base "

"class, which is :class:`object` by default. Most types use the default "

"allocation strategy."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:364

msgid ""

"If you are creating a co-operative :c:member:`~PyTypeObject.tp_new` (one "

"that calls a base type's :c:member:`~PyTypeObject.tp_new` or :meth:`~object."

"__new__`), you must *not* try to determine what method to call using method "

"resolution order at runtime. Always statically determine what type you are "

"going to call, and call its :c:member:`~PyTypeObject.tp_new` directly, or "

"via ``type->tp_base->tp_new``. If you do not do this, Python subclasses of "

"your type that also inherit from other Python-defined classes may not work "

"correctly. (Specifically, you may not be able to create instances of such "

"subclasses without getting a :exc:`TypeError`.)"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:374

msgid ""

"We also define an initialization function which accepts arguments to provide "

"initial values for our instance::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:377

msgid ""

"static int\n"

"Custom_init(PyObject *op, PyObject *args, PyObject *kwds)\n"

"{\n"

" CustomObject *self = (CustomObject *) op;\n"

" static char *kwlist[] = {\"first\", \"last\", \"number\", NULL};\n"

" PyObject *first = NULL, *last = NULL, *tmp;\n"

"\n"

" if (!PyArg_ParseTupleAndKeywords(args, kwds, \"|OOi\", kwlist,\n"

" &first, &last,\n"

" &self->number))\n"

" return -1;\n"

"\n"

" if (first) {\n"

" tmp = self->first;\n"

" Py_INCREF(first);\n"

" self->first = first;\n"

" Py_XDECREF(tmp);\n"

" }\n"

" if (last) {\n"

" tmp = self->last;\n"

" Py_INCREF(last);\n"

" self->last = last;\n"

" Py_XDECREF(tmp);\n"

" }\n"

" return 0;\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:404

msgid "by filling the :c:member:`~PyTypeObject.tp_init` slot. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:406

msgid ".tp_init = Custom_init,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:408

msgid ""

"The :c:member:`~PyTypeObject.tp_init` slot is exposed in Python as the :meth:"

"`~object.__init__` method. It is used to initialize an object after it's "

"created. Initializers always accept positional and keyword arguments, and "

"they should return either ``0`` on success or ``-1`` on error."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:413

msgid ""

"Unlike the ``tp_new`` handler, there is no guarantee that ``tp_init`` is "

"called at all (for example, the :mod:`pickle` module by default doesn't "

"call :meth:`~object.__init__` on unpickled instances). It can also be "

"called multiple times. Anyone can call the :meth:`!__init__` method on our "

"objects. For this reason, we have to be extra careful when assigning the "

"new attribute values. We might be tempted, for example to assign the "

"``first`` member like this::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:421

msgid ""

"if (first) {\n"

" Py_XDECREF(self->first);\n"

" Py_INCREF(first);\n"

" self->first = first;\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:427

msgid ""

"But this would be risky. Our type doesn't restrict the type of the "

"``first`` member, so it could be any kind of object. It could have a "

"destructor that causes code to be executed that tries to access the "

"``first`` member; or that destructor could detach the :term:`thread state "

"<attached thread state>` and let arbitrary code run in other threads that "

"accesses and modifies our object."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:434

msgid ""

"To be paranoid and protect ourselves against this possibility, we almost "

"always reassign members before decrementing their reference counts. When "

"don't we have to do this?"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:438

msgid "when we absolutely know that the reference count is greater than 1;"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:440

msgid ""

"when we know that deallocation of the object [#]_ will neither detach the :"

"term:`thread state <attached thread state>` nor cause any calls back into "

"our type's code;"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:443

msgid ""

"when decrementing a reference count in a :c:member:`~PyTypeObject."

"tp_dealloc` handler on a type which doesn't support cyclic garbage "

"collection [#]_."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:446

msgid ""

"We want to expose our instance variables as attributes. There are a number "

"of ways to do that. The simplest way is to define member definitions::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:449

msgid ""

"static PyMemberDef Custom_members[] = {\n"

" {\"first\", Py_T_OBJECT_EX, offsetof(CustomObject, first), 0,\n"

" \"first name\"},\n"

" {\"last\", Py_T_OBJECT_EX, offsetof(CustomObject, last), 0,\n"

" \"last name\"},\n"

" {\"number\", Py_T_INT, offsetof(CustomObject, number), 0,\n"

" \"custom number\"},\n"

" {NULL} /* Sentinel */\n"

"};"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:459

msgid ""

"and put the definitions in the :c:member:`~PyTypeObject.tp_members` slot::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:461

msgid ".tp_members = Custom_members,"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:463

msgid ""

"Each member definition has a member name, type, offset, access flags and "

"documentation string. See the :ref:`Generic-Attribute-Management` section "

"below for details."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:467

msgid ""

"A disadvantage of this approach is that it doesn't provide a way to restrict "

"the types of objects that can be assigned to the Python attributes. We "

"expect the first and last names to be strings, but any Python objects can be "

"assigned. Further, the attributes can be deleted, setting the C pointers to "

"``NULL``. Even though we can make sure the members are initialized to non-"

"``NULL`` values, the members can be set to ``NULL`` if the attributes are "

"deleted."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:474

msgid ""

"We define a single method, :meth:`!Custom.name`, that outputs the objects "

"name as the concatenation of the first and last names. ::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:477

msgid ""

"static PyObject *\n"

"Custom_name(PyObject *op, PyObject *Py_UNUSED(dummy))\n"

"{\n"

" CustomObject *self = (CustomObject *) op;\n"

" if (self->first == NULL) {\n"

" PyErr_SetString(PyExc_AttributeError, \"first\");\n"

" return NULL;\n"

" }\n"

" if (self->last == NULL) {\n"

" PyErr_SetString(PyExc_AttributeError, \"last\");\n"

" return NULL;\n"

" }\n"

" return PyUnicode_FromFormat(\"%S %S\", self->first, self->last);\n"

"}"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:492

msgid ""

"The method is implemented as a C function that takes a :class:`!Custom` (or :"

"class:`!Custom` subclass) instance as the first argument. Methods always "

"take an instance as the first argument. Methods often take positional and "

"keyword arguments as well, but in this case we don't take any and don't need "

"to accept a positional argument tuple or keyword argument dictionary. This "

"method is equivalent to the Python method:"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:499

msgid ""

"def name(self):\n"

" return \"%s %s\" % (self.first, self.last)"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:504

msgid ""

"Note that we have to check for the possibility that our :attr:`!first` and :"

"attr:`!last` members are ``NULL``. This is because they can be deleted, in "

"which case they are set to ``NULL``. It would be better to prevent deletion "

"of these attributes and to restrict the attribute values to be strings. "

"We'll see how to do that in the next section."

msgstr ""

#: ../../extending/newtypes_tutorial.rst:510

msgid ""

"Now that we've defined the method, we need to create an array of method "

"definitions::"

msgstr ""

#: ../../extending/newtypes_tutorial.rst:513

msgid ""

"static PyMethodDef Custom_methods[] = {\n"

" {\"name\", Custom_name, METH_NOARGS,\n"

" \"Return the name, combining the first and last name\"\n"