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#
SOME DESCRIPTIVE TITLE.
#
Copyright (C) 2001 Python Software Foundation
#
This file is distributed under the same license as the Python package.
#
FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
#
Translators:
#
python-doc bot, 2025
#
msgid ""
msgstr ""
"
Project-Id-Version
:
Python 3.14\n
"
"
Report-Msgid-Bugs-To
:
\n
"
"
POT-Creation-Date
:
2026-09-05 16:53+0200\n
"
"
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"
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