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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:
# Bhuvansh Kataria, 2026
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: Python 3.15\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2026-07-31 15:58+0000\n"
"PO-Revision-Date: 2025-09-16 00:00+0000\n"
"Last-Translator: Bhuvansh Kataria, 2026\n"
"Language-Team: Panjabi (Punjabi) (https://app.transifex.com/python-doc/"
"teams/5390/pa/)\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Language: pa\n"
"Plural-Forms: nplurals=2; plural=(n != 1);\n"
msgid "Introduction"
msgstr ""
msgid ""
"The Application Programmer's Interface to Python gives C and C++ programmers "
"access to the Python interpreter at a variety of levels. The API is equally "
"usable from C++, but for brevity it is generally referred to as the Python/C "
"API. There are two fundamentally different reasons for using the Python/C "
"API. The first reason is to write *extension modules* for specific purposes; "
"these are C modules that extend the Python interpreter. This is probably "
"the most common use. The second reason is to use Python as a component in a "
"larger application; this technique is generally referred to as :dfn:"
"`embedding` Python in an application."
msgstr ""
msgid ""
"Writing an extension module is a relatively well-understood process, where a "
"\"cookbook\" approach works well. There are several tools that automate the "
"process to some extent. While people have embedded Python in other "
"applications since its early existence, the process of embedding Python is "
"less straightforward than writing an extension."
msgstr ""
msgid ""
"Many API functions are useful independent of whether you're embedding or "
"extending Python; moreover, most applications that embed Python will need "
"to provide a custom extension as well, so it's probably a good idea to "
"become familiar with writing an extension before attempting to embed Python "
"in a real application."
msgstr ""
msgid "Language version compatibility"
msgstr ""
msgid "Python's C API is compatible with C11 and C++11 versions of C and C++."
msgstr ""
msgid ""
"This is a lower limit: the C API does not require features from later C/C++ "
"versions. You do *not* need to enable your compiler's \"c11 mode\"."
msgstr ""
msgid "Coding standards"
msgstr ""
msgid ""
"If you're writing C code for inclusion in CPython, you **must** follow the "
"guidelines and standards defined in :PEP:`7`. These guidelines apply "
"regardless of the version of Python you are contributing to. Following "
"these conventions is not necessary for your own third party extension "
"modules, unless you eventually expect to contribute them to Python."
msgstr ""
msgid "Include Files"
msgstr ""
msgid ""
"All function, type and macro definitions needed to use the Python/C API are "
"included in your code by the following line::"
msgstr ""
msgid ""
"#define PY_SSIZE_T_CLEAN\n"
"#include <Python.h>"
msgstr ""
msgid ""
"This implies inclusion of the following standard headers: ``<stdio.h>``, "
"``<string.h>``, ``<errno.h>``, ``<limits.h>``, ``<assert.h>`` and ``<stdlib."
"h>`` (if available)."
msgstr ""
msgid ""
"Since Python may define some pre-processor definitions which affect the "
"standard headers on some systems, you *must* include :file:`Python.h` before "
"any standard headers are included."
msgstr ""
msgid ""
"It is recommended to always define ``PY_SSIZE_T_CLEAN`` before including "
"``Python.h``. See :ref:`arg-parsing` for a description of this macro."
msgstr ""
msgid ""
"All user visible names defined by Python.h (except those defined by the "
"included standard headers) have one of the prefixes ``Py`` or ``_Py``. "
"Names beginning with ``_Py`` are for internal use by the Python "
"implementation and should not be used by extension writers. Structure member "
"names do not have a reserved prefix."
msgstr ""
msgid ""
"User code should never define names that begin with ``Py`` or ``_Py``. This "
"confuses the reader, and jeopardizes the portability of the user code to "
"future Python versions, which may define additional names beginning with one "
"of these prefixes."
msgstr ""
msgid ""
"The header files are typically installed with Python. On Unix, these are "
"located in the directories :file:`{prefix}/include/pythonversion/` and :file:"
"`{exec_prefix}/include/pythonversion/`, where :option:`prefix <--prefix>` "
"and :option:`exec_prefix <--exec-prefix>` are defined by the corresponding "
"parameters to Python's :program:`configure` script and *version* is ``'%d."
"%d' % sys.version_info[:2]``. On Windows, the headers are installed in :"
"file:`{prefix}/include`, where ``prefix`` is the installation directory "
"specified to the installer."
msgstr ""
msgid ""
"To include the headers, place both directories (if different) on your "
"compiler's search path for includes. Do *not* place the parent directories "
"on the search path and then use ``#include <pythonX.Y/Python.h>``; this will "
"break on multi-platform builds since the platform independent headers under :"
"option:`prefix <--prefix>` include the platform specific headers from :"
"option:`exec_prefix <--exec-prefix>`."
msgstr ""
msgid ""
"C++ users should note that although the API is defined entirely using C, the "
"header files properly declare the entry points to be ``extern \"C\"``. As a "
"result, there is no need to do anything special to use the API from C++."
msgstr ""
msgid "System includes"
msgstr ""
msgid ""
":file:`Python.h` includes several standard header files. C extensions should "
"include the standard headers that they use, and should not rely on these "
"implicit includes. The implicit includes are:"
msgstr ""
msgid "``<assert.h>``"
msgstr ""
msgid "``<intrin.h>`` (on Windows)"
msgstr ""
msgid "``<inttypes.h>``"
msgstr ""
msgid "``<limits.h>``"
msgstr ""
msgid "``<math.h>``"
msgstr ""
msgid "``<stdarg.h>``"
msgstr ""
msgid "``<string.h>``"
msgstr ""
msgid "``<wchar.h>``"
msgstr ""
msgid "``<sys/types.h>`` (if present)"
msgstr ""
msgid ""
"The following are included for backwards compatibility, unless using :ref:"
"`Limited API <limited-c-api>` 3.13 or newer:"
msgstr ""
msgid "``<ctype.h>``"
msgstr ""
msgid "``<unistd.h>`` (on POSIX)"
msgstr ""
msgid ""
"The following are included for backwards compatibility, unless using :ref:"
"`Limited API <limited-c-api>` 3.11 or newer:"
msgstr ""
msgid "``<errno.h>``"
msgstr ""
msgid "``<stdio.h>``"
msgstr ""
msgid "``<stdlib.h>``"
msgstr ""
msgid "Useful macros"
msgstr ""
msgid ""
"Several useful macros are defined in the Python header files. Many are "
"defined closer to where they are useful (for example, :c:macro:"
"`Py_RETURN_NONE`, :c:macro:`PyMODINIT_FUNC`). Others of a more general "
"utility are defined here. This is not necessarily a complete listing."
msgstr ""
msgid ""
"If this macro is defined, then the current system is able to start threads."
msgstr ""
msgid ""
"Currently, all systems supported by CPython (per :pep:`11`), with the "
"exception of some WebAssembly platforms, support starting threads."
msgstr ""
msgid ""
"Like :samp:`getenv({s})`, but returns ``NULL`` if :option:`-E` was passed on "
"the command line (see :c:member:`PyConfig.use_environment`)."
msgstr ""
msgid "Docstring macros"
msgstr ""
msgid ""
"Creates a variable with name *name* that can be used in docstrings. If "
"Python is built without docstrings (:option:`--without-doc-strings`), the "
"value will be an empty string."
msgstr ""
msgid "Example::"
msgstr ""
msgid ""
"PyDoc_STRVAR(pop_doc, \"Remove and return the rightmost element.\");\n"
"\n"
"static PyMethodDef deque_methods[] = {\n"
" // ...\n"
" {\"pop\", (PyCFunction)deque_pop, METH_NOARGS, pop_doc},\n"
" // ...\n"
"}"
msgstr ""
msgid "Expands to :samp:`PyDoc_VAR({name}) = PyDoc_STR({str})`."
msgstr ""
msgid ""
"Expands to the given input string, or an empty string if docstrings are "
"disabled (:option:`--without-doc-strings`)."
msgstr ""
msgid ""
"static PyMethodDef pysqlite_row_methods[] = {\n"
" {\"keys\", (PyCFunction)pysqlite_row_keys, METH_NOARGS,\n"
" PyDoc_STR(\"Returns the keys of the row.\")},\n"
" {NULL, NULL}\n"
"};"
msgstr ""
msgid ""
"Declares a static character array variable with the given *name*. Expands "
"to :samp:`static const char {name}[]`"
msgstr ""
msgid "For example::"
msgstr ""
msgid ""
"PyDoc_VAR(python_doc) = PyDoc_STR(\n"
" \"A genus of constricting snakes in the Pythonidae family native \"\n"
" \"to the tropics and subtropics of the Eastern Hemisphere.\");"
msgstr ""
msgid "General utility macros"
msgstr ""
msgid "The following macros are for common tasks not specific to Python."
msgstr ""
msgid ""
"Use this for unused arguments in a function definition to silence compiler "
"warnings. Example: ``int func(int a, int Py_UNUSED(b)) { return a; }``."
msgstr ""
msgid ""
"Use a GCC attribute *name*, hiding it from compilers that don't support GCC "
"attributes (such as MSVC)."
msgstr ""
msgid ""
"This expands to :samp:`__attribute__(({name)})` on a GCC compiler, and "
"expands to nothing on compilers that don't support GCC attributes."
msgstr ""
msgid "Numeric utilities"
msgstr ""
msgid "Return the absolute value of ``x``."
msgstr ""
msgid ""
"The argument may be evaluated more than once. Consequently, do not pass an "
"expression with side-effects directly to this macro."
msgstr ""
msgid ""
"If the result cannot be represented (for example, if ``x`` has :c:macro:`!"
"INT_MIN` value for :c:expr:`int` type), the behavior is undefined."
msgstr ""
msgid "Corresponds roughly to :samp:`(({x}) < 0 ? -({x}) : ({x}))`"
msgstr ""
msgid "Return the larger or smaller of the arguments, respectively."
msgstr ""
msgid ""
"Any arguments may be evaluated more than once. Consequently, do not pass an "
"expression with side-effects directly to this macro."
msgstr ""
msgid ""
":c:macro:`!Py_MAX` corresponds roughly to :samp:`((({x}) > ({y})) ? ({x}) : "
"({y}))`."
msgstr ""
msgid ""
"Similar to :samp:`{integer} >> {positions}`, but forces sign extension, as "
"the C standard does not define whether a right-shift of a signed integer "
"will perform sign extension or a zero-fill."
msgstr ""
msgid ""
"*integer* should be any signed integer type. *positions* is the number of "
"positions to shift to the right."
msgstr ""
msgid ""
"Both *integer* and *positions* can be evaluated more than once; "
"consequently, avoid directly passing a function call or some other operation "
"with side-effects to this macro. Instead, store the result as a variable and "
"then pass it."
msgstr ""
msgid ""
"*type* is unused and only kept for backwards compatibility. Historically, "
"*type* was used to cast *integer*."
msgstr ""
msgid ""
"This macro is now valid for all signed integer types, not just those for "
"which ``unsigned type`` is legal. As a result, *type* is no longer used."
msgstr ""
msgid ""
"Argument must be a character or an integer in the range [-128, 127] or [0, "
"255]. This macro returns ``c`` cast to an ``unsigned char``."
msgstr ""
msgid "Assertion utilities"
msgstr ""
msgid ""
"Use this when you have a code path that cannot be reached by design. For "
"example, in the ``default:`` clause in a ``switch`` statement for which all "
"possible values are covered in ``case`` statements. Use this in places "
"where you might be tempted to put an ``assert(0)`` or ``abort()`` call."
msgstr ""
msgid ""
"In release mode, the macro helps the compiler to optimize the code, and "
"avoids a warning about unreachable code. For example, the macro is "
"implemented with ``__builtin_unreachable()`` on GCC in release mode."
msgstr ""
msgid ""
"In debug mode, and on unsupported compilers, the macro expands to a call to :"
"c:func:`Py_FatalError`."
msgstr ""
msgid ""
"A use for ``Py_UNREACHABLE()`` is following a call to a function that never "
"returns but that is not declared ``_Noreturn``."
msgstr ""
msgid ""
"If a code path is very unlikely code but can be reached under exceptional "
"case, this macro must not be used. For example, under low memory condition "
"or if a system call returns a value out of the expected range. In this "
"case, it's better to report the error to the caller. If the error cannot be "
"reported to caller, :c:func:`Py_FatalError` can be used."
msgstr ""
msgid ""
"Cast *value* to type *smaller* from type *larger*, validating that no "
"information was lost."
msgstr ""
msgid ""
"On release builds of Python, this is roughly equivalent to :samp:"
"`(({smaller}) {value})` (in C++, :samp:`static_cast<{smaller}>({value})` "
"will be used instead)."
msgstr ""
msgid ""
"On debug builds (implying that :c:macro:`Py_DEBUG` is defined), this asserts "
"that no information was lost with the cast from *larger* to *smaller*."
msgstr ""
msgid ""
"*value*, *larger*, and *smaller* may all be evaluated more than once in the "
"expression; consequently, do not pass an expression with side-effects "
"directly to this macro."
msgstr ""
msgid ""
"Asserts a compile-time condition *cond*, as a statement. The build will fail "
"if the condition is false or cannot be evaluated at compile time."
msgstr ""
msgid "Corresponds roughly to :samp:`static_assert({cond})` on C23 and above."
msgstr ""
msgid "Py_BUILD_ASSERT(sizeof(PyTime_t) == sizeof(int64_t));"
msgstr ""
msgid ""
"Asserts a compile-time condition *cond*, as an expression that evaluates to "
"``0``. The build will fail if the condition is false or cannot be evaluated "
"at compile time."
msgstr ""
msgid ""
"#define foo_to_char(foo) \\\n"
" ((char *)(foo) + Py_BUILD_ASSERT_EXPR(offsetof(struct foo, string) == 0))"
msgstr ""
msgid "Type size utilities"
msgstr ""
msgid "Compute the length of a statically allocated C array at compile time."
msgstr ""
msgid ""
"The *array* argument must be a C array with a size known at compile time. "
"Passing an array with an unknown size, such as a heap-allocated array, will "
"result in a compilation error on some compilers, or otherwise produce "
"incorrect results."
msgstr ""
msgid "This is roughly equivalent to::"
msgstr ""
msgid "sizeof(array) / sizeof((array)[0])"
msgstr ""
msgid "Return the size of a structure (*type*) *member* in bytes."
msgstr ""
msgid "Corresponds roughly to :samp:`sizeof((({type} *)NULL)->{member})`."
msgstr ""
msgid "Macro definition utilities"
msgstr ""
msgid ""
"This is equivalent to :samp:`{X}`, which is useful for token-pasting in "
"macros, as macro expansions in *X* are forcefully evaluated by the "
"preprocessor."
msgstr ""
msgid ""
"Convert ``x`` to a C string. For example, ``Py_STRINGIFY(123)`` returns "
"``\"123\"``."
msgstr ""
msgid "Declaration utilities"
msgstr ""
msgid ""
"The following macros can be used in declarations. They are most useful for "
"defining the C API itself, and have limited use for extension authors. Most "
"of them expand to compiler-specific spellings of common extensions to the C "
"language."
msgstr ""
msgid ""
"Ask the compiler to always inline a static inline function. The compiler can "
"ignore it and decide to not inline the function."
msgstr ""
msgid ""
"Corresponds to ``always_inline`` attribute in GCC and ``__forceinline`` in "
"MSVC."
msgstr ""
msgid ""
"It can be used to inline performance critical static inline functions when "
"building Python in debug mode with function inlining disabled. For example, "
"MSC disables function inlining when building in debug mode."
msgstr ""
msgid ""
"Marking blindly a static inline function with Py_ALWAYS_INLINE can result in "
"worse performances (due to increased code size for example). The compiler is "
"usually smarter than the developer for the cost/benefit analysis."
msgstr ""
msgid ""
"If Python is :ref:`built in debug mode <debug-build>` (if the :c:macro:"
"`Py_DEBUG` macro is defined), the :c:macro:`Py_ALWAYS_INLINE` macro does "
"nothing."
msgstr ""
msgid "It must be specified before the function return type. Usage::"
msgstr ""
msgid "static inline Py_ALWAYS_INLINE int random(void) { return 4; }"
msgstr ""
msgid ""
"Disable inlining on a function. For example, it reduces the C stack "
"consumption: useful on LTO+PGO builds which heavily inline code (see :issue:"
"`33720`)."
msgstr ""
msgid ""
"Corresponds to the ``noinline`` attribute/specification on GCC and MSVC."
msgstr ""
msgid "Usage::"
msgstr ""
msgid "Py_NO_INLINE static int random(void) { return 4; }"
msgstr ""
msgid ""
"Use this to declare APIs that were deprecated in a specific CPython version. "
"The macro must be placed before the symbol name."
msgstr ""
msgid "Py_DEPRECATED(3.8) PyAPI_FUNC(int) Py_OldFunction(void);"
msgstr ""
msgid "MSVC support was added."
msgstr ""
msgid ""
"Declare a function returning the specified *type* using a fast-calling "
"qualifier for functions that are local to the current file. Semantically, "
"this is equivalent to :samp:`static {type}`."
msgstr ""
msgid ""
"Equivalent to :c:macro:`Py_LOCAL` but additionally requests the function be "
"inlined."
msgstr ""
msgid ""
"Macro used to declare a symbol as local to the shared library (hidden). On "
"supported platforms, it ensures the symbol is not exported."
msgstr ""
msgid ""
"On compatible versions of GCC/Clang, it expands to "
"``__attribute__((visibility(\"hidden\")))``."
msgstr ""
msgid ""
"Macro used to declare a symbol (function or data) as exported. On Windows, "
"this expands to ``__declspec(dllexport)``. On compatible versions of GCC/"
"Clang, it expands to ``__attribute__((visibility(\"default\")))``. This "
"macro is for defining the C API itself; extension modules should not use it."
msgstr ""
msgid ""
"Macro used to declare a symbol as imported. On Windows, this expands to "
"``__declspec(dllimport)``. This macro is for defining the C API itself; "
"extension modules should not use it."
msgstr ""
msgid ""
"Macro used by CPython to declare a function as part of the C API. Its "
"expansion depends on the platform and build configuration. This macro is "
"intended for defining CPython's C API itself; extension modules should not "
"use it for their own symbols."
msgstr ""
msgid ""
"Macro used by CPython to declare a public global variable as part of the C "
"API. Its expansion depends on the platform and build configuration. This "
"macro is intended for defining CPython's C API itself; extension modules "
"should not use it for their own symbols."
msgstr ""
msgid "Outdated macros"
msgstr ""
msgid ""
"The following :term:`soft deprecated` macros have been used to features that "
"have been standardized in C11 (or previous standards)."
msgstr ""
msgid ""
"On some GCC-like compilers, specify alignment to *num* bytes. This does "
"nothing on other compilers."
msgstr ""
msgid "Use the standard ``alignas`` specifier rather than this macro."
msgstr ""
msgid ""
"The :c:func:`printf` formatting modifier for :c:type:`size_t`. Use ``\"z\"`` "
"directly instead."
msgstr ""
msgid ""
"Use *number* as a ``long long`` or ``unsigned long long`` integer literal, "
"respectively."
msgstr ""
msgid ""
"Expands to *number* followed by ``LL`` or ``LLU``, respectively, but will "
"expand to some compiler-specific suffixes on some older compilers."
msgstr ""
msgid "Consider using the C99 standard suffixes ``LL`` and ``LLU`` directly."
msgstr ""
msgid ""
"Aliases for the types :c:type:`!long long`, :c:type:`!int32_t`, :c:type:`!"
"uint32_t`. :c:type:`!int64_t` and :c:type:`!uint64_t`, respectively. "
"Historically, these types needed compiler-specific extensions."
msgstr ""
msgid ""
"Aliases for the values :c:macro:`!LLONG_MIN`, :c:macro:`!LLONG_MAX`, :c:"
"macro:`!ULLONG_MAX`, and :c:macro:`!SIZE_MAX`, respectively. Use these "
"standard names instead."
msgstr ""
msgid ""
"The required header, ``<limits.h>``, :ref:`is included <capi-system-"
"includes>` in ``Python.h``."
msgstr ""
msgid "This is an alias to :c:func:`!memcpy`."
msgstr ""
msgid "Use :c:func:`!memcpy` directly instead."
msgstr ""
msgid ""
"Size of the :c:type:`!wchar_t` type. Use ``sizeof(wchar_t)`` or "
"``WCHAR_WIDTH/8`` instead."
msgstr ""
msgid ""
"The required header for the latter, ``<limits.h>``, :ref:`is included <capi-"
"system-includes>` in ``Python.h``."
msgstr ""
msgid ""
"Defined if ``wchar_t`` can hold a Unicode character (UCS-4). Use "
"``sizeof(wchar_t) >= 4`` instead"
msgstr ""
msgid "This is an alias to the C99-standard ``va_copy`` function."
msgstr ""
msgid ""
"Historically, this would use a compiler-specific method to copy a "
"``va_list``."
msgstr ""
msgid "This is now an alias to ``va_copy``."
msgstr ""
msgid "Objects, Types and Reference Counts"
msgstr ""
msgid ""
"Most Python/C API functions have one or more arguments as well as a return "
"value of type :c:expr:`PyObject*`. This type is a pointer to an opaque data "
"type representing an arbitrary Python object. Since all Python object types "
"are treated the same way by the Python language in most situations (e.g., "
"assignments, scope rules, and argument passing), it is only fitting that "
"they should be represented by a single C type. Almost all Python objects "
"live on the heap: you never declare an automatic or static variable of type :"
"c:type:`PyObject`, only pointer variables of type :c:expr:`PyObject*` can "
"be declared. The sole exception are the type objects; since these must "
"never be deallocated, they are typically static :c:type:`PyTypeObject` "
"objects."
msgstr ""
msgid ""
"All Python objects (even Python integers) have a :dfn:`type` and a :dfn:"
"`reference count`. An object's type determines what kind of object it is (e."
"g., an integer, a list, or a user-defined function; there are many more as "
"explained in :ref:`types`). For each of the well-known types there is a "
"macro to check whether an object is of that type; for instance, "
"``PyList_Check(a)`` is true if (and only if) the object pointed to by *a* is "
"a Python list."
msgstr ""
msgid "Reference Counts"
msgstr ""
msgid ""
"The reference count is important because today's computers have a finite "
"(and often severely limited) memory size; it counts how many different "
"places there are that have a :term:`strong reference` to an object. Such a "
"place could be another object, or a global (or static) C variable, or a "
"local variable in some C function. When the last :term:`strong reference` to "
"an object is released (i.e. its reference count becomes zero), the object is "
"deallocated. If it contains references to other objects, those references "
"are released. Those other objects may be deallocated in turn, if there are "
"no more references to them, and so on. (There's an obvious problem with "
"objects that reference each other here; for now, the solution is \"don't do "
"that.\")"
msgstr ""
msgid ""
"Reference counts are always manipulated explicitly. The normal way is to "
"use the macro :c:func:`Py_INCREF` to take a new reference to an object (i.e. "
"increment its reference count by one), and :c:func:`Py_DECREF` to release "
"that reference (i.e. decrement the reference count by one). The :c:func:"
"`Py_DECREF` macro is considerably more complex than the incref one, since it "
"must check whether the reference count becomes zero and then cause the "
"object's deallocator to be called. The deallocator is a function pointer "
"contained in the object's type structure. The type-specific deallocator "
"takes care of releasing references for other objects contained in the object "
"if this is a compound object type, such as a list, as well as performing any "
"additional finalization that's needed. There's no chance that the reference "
"count can overflow; at least as many bits are used to hold the reference "
"count as there are distinct memory locations in virtual memory (assuming "
"``sizeof(Py_ssize_t) >= sizeof(void*)``). Thus, the reference count "
"increment is a simple operation."
msgstr ""
msgid ""
"It is not necessary to hold a :term:`strong reference` (i.e. increment the "
"reference count) for every local variable that contains a pointer to an "
"object. In theory, the object's reference count goes up by one when the "
"variable is made to point to it and it goes down by one when the variable "
"goes out of scope. However, these two cancel each other out, so at the end "
"the reference count hasn't changed. The only real reason to use the "
"reference count is to prevent the object from being deallocated as long as "
"our variable is pointing to it. If we know that there is at least one "
"other reference to the object that lives at least as long as our variable, "
"there is no need to take a new :term:`strong reference` (i.e. increment the "
"reference count) temporarily. An important situation where this arises is in "
"objects that are passed as arguments to C functions in an extension module "
"that are called from Python; the call mechanism guarantees to hold a "
"reference to every argument for the duration of the call."
msgstr ""
msgid ""
"However, a common pitfall is to extract an object from a list and hold on to "
"it for a while without taking a new reference. Some other operation might "
"conceivably remove the object from the list, releasing that reference, and "
"possibly deallocating it. The real danger is that innocent-looking "
"operations may invoke arbitrary Python code which could do this; there is a "
"code path which allows control to flow back to the user from a :c:func:"
"`Py_DECREF`, so almost any operation is potentially dangerous."
msgstr ""
msgid ""
"A safe approach is to always use the generic operations (functions whose "
"name begins with ``PyObject_``, ``PyNumber_``, ``PySequence_`` or "
"``PyMapping_``). These operations always create a new :term:`strong "
"reference` (i.e. increment the reference count) of the object they return. "
"This leaves the caller with the responsibility to call :c:func:`Py_DECREF` "
"when they are done with the result; this soon becomes second nature."
msgstr ""
msgid "Reference Count Details"
msgstr ""
msgid ""
"The reference count behavior of functions in the Python/C API is best "
"explained in terms of *ownership of references*. Ownership pertains to "
"references, never to objects (objects are not owned: they are always "
"shared). \"Owning a reference\" means being responsible for calling "
"Py_DECREF on it when the reference is no longer needed. Ownership can also "
"be transferred, meaning that the code that receives ownership of the "
"reference then becomes responsible for eventually releasing it by calling :c:"
"func:`Py_DECREF` or :c:func:`Py_XDECREF` when it's no longer needed---or "
"passing on this responsibility (usually to its caller). When a function "
"passes ownership of a reference on to its caller, the caller is said to "
"receive a *new* reference. When no ownership is transferred, the caller is "
"said to *borrow* the reference. Nothing needs to be done for a :term:"
"`borrowed reference`."
msgstr ""
msgid ""
"Conversely, when a calling function passes in a reference to an object, "
"there are two possibilities: the function *steals* a reference to the "
"object, or it does not."
msgstr ""
msgid ""
"*Stealing a reference* means that when you pass a reference to a function, "
"that function assumes that it now owns that reference. Since the new owner "
"can use :c:func:`!Py_DECREF` at its discretion, you (the caller) must not "
"use that reference after the call."
msgstr ""
msgid ""
"Few functions steal references; the two notable exceptions are :c:func:"
"`PyList_SetItem` and :c:func:`PyTuple_SetItem`, which steal a reference to "
"the item (but not to the tuple or list into which the item is put!). These "
"functions were designed to steal a reference because of a common idiom for "
"populating a tuple or list with newly created objects; for example, the code "
"to create the tuple ``(1, 2, \"three\")`` could look like this (forgetting "
"about error handling for the moment; a better way to code this is shown "
"below)::"
msgstr ""
msgid ""
"PyObject *t;\n"
"\n"
"t = PyTuple_New(3);\n"
"PyTuple_SetItem(t, 0, PyLong_FromLong(1L));\n"
"PyTuple_SetItem(t, 1, PyLong_FromLong(2L));\n"
"PyTuple_SetItem(t, 2, PyUnicode_FromString(\"three\"));"
msgstr ""
msgid ""
"Here, :c:func:`PyLong_FromLong` returns a new reference which is immediately "
"stolen by :c:func:`PyTuple_SetItem`. When you want to keep using an object "
"although the reference to it will be stolen, use :c:func:`Py_INCREF` to grab "
"another reference before calling the reference-stealing function."
msgstr ""
msgid ""
"Incidentally, :c:func:`PyTuple_SetItem` is the *only* way to set tuple "
"items; :c:func:`PySequence_SetItem` and :c:func:`PyObject_SetItem` refuse to "
"do this since tuples are an immutable data type. You should only use :c:"
"func:`PyTuple_SetItem` for tuples that you are creating yourself."
msgstr ""
msgid ""
"Equivalent code for populating a list can be written using :c:func:"
"`PyList_New` and :c:func:`PyList_SetItem`."
msgstr ""
msgid ""
"However, in practice, you will rarely use these ways of creating and "
"populating a tuple or list. There's a generic function, :c:func:"
"`Py_BuildValue`, that can create most common objects from C values, directed "
"by a :dfn:`format string`. For example, the above two blocks of code could "
"be replaced by the following (which also takes care of the error checking)::"
msgstr ""
msgid ""
"PyObject *tuple, *list;\n"
"\n"
"tuple = Py_BuildValue(\"(iis)\", 1, 2, \"three\");\n"
"list = Py_BuildValue(\"[iis]\", 1, 2, \"three\");"
msgstr ""
msgid ""
"It is much more common to use :c:func:`PyObject_SetItem` and friends with "
"items whose references you are only borrowing, like arguments that were "
"passed in to the function you are writing. In that case, their behaviour "
"regarding references is much saner, since you don't have to take a new "
"reference just so you can give that reference away (\"have it be stolen\"). "
"For example, this function sets all items of a list (actually, any mutable "
"sequence) to a given item::"
msgstr ""
msgid ""
"int\n"
"set_all(PyObject *target, PyObject *item)\n"
"{\n"
" Py_ssize_t i, n;\n"
"\n"
" n = PyObject_Length(target);\n"
" if (n < 0)\n"
" return -1;\n"
" for (i = 0; i < n; i++) {\n"
" PyObject *index = PyLong_FromSsize_t(i);\n"
" if (!index)\n"
" return -1;\n"
" if (PyObject_SetItem(target, index, item) < 0) {\n"
" Py_DECREF(index);\n"
" return -1;\n"
" }\n"
" Py_DECREF(index);\n"
" }\n"
" return 0;\n"
"}"
msgstr ""
msgid ""
"The situation is slightly different for function return values. While "
"passing a reference to most functions does not change your ownership "
"responsibilities for that reference, many functions that return a reference "
"to an object give you ownership of the reference. The reason is simple: in "
"many cases, the returned object is created on the fly, and the reference "
"you get is the only reference to the object. Therefore, the generic "
"functions that return object references, like :c:func:`PyObject_GetItem` "
"and :c:func:`PySequence_GetItem`, always return a new reference (the caller "
"becomes the owner of the reference)."
msgstr ""
msgid ""
"It is important to realize that whether you own a reference returned by a "
"function depends on which function you call only --- *the plumage* (the type "
"of the object passed as an argument to the function) *doesn't enter into it!"
"* Thus, if you extract an item from a list using :c:func:`PyList_GetItem`, "
"you don't own the reference --- but if you obtain the same item from the "
"same list using :c:func:`PySequence_GetItem` (which happens to take exactly "
"the same arguments), you do own a reference to the returned object."
msgstr ""
msgid ""
"Here is an example of how you could write a function that computes the sum "
"of the items in a list of integers; once using :c:func:`PyList_GetItem`, "
"and once using :c:func:`PySequence_GetItem`. ::"
msgstr ""
msgid ""
"long\n"
"sum_list(PyObject *list)\n"
"{\n"
" Py_ssize_t i, n;\n"
" long total = 0, value;\n"
" PyObject *item;\n"
"\n"
" n = PyList_Size(list);\n"
" if (n < 0)\n"
" return -1; /* Not a list */\n"
" for (i = 0; i < n; i++) {\n"
" item = PyList_GetItem(list, i); /* Can't fail */\n"
" if (!PyLong_Check(item)) continue; /* Skip non-integers */\n"
" value = PyLong_AsLong(item);\n"
" if (value == -1 && PyErr_Occurred())\n"
" /* Integer too big to fit in a C long, bail out */\n"
" return -1;\n"
" total += value;\n"
" }\n"
" return total;\n"
"}"
msgstr ""
msgid ""
"long\n"
"sum_sequence(PyObject *sequence)\n"
"{\n"
" Py_ssize_t i, n;\n"
" long total = 0, value;\n"
" PyObject *item;\n"
" n = PySequence_Length(sequence);\n"
" if (n < 0)\n"
" return -1; /* Has no length */\n"
" for (i = 0; i < n; i++) {\n"
" item = PySequence_GetItem(sequence, i);\n"
" if (item == NULL)\n"
" return -1; /* Not a sequence, or other failure */\n"
" if (PyLong_Check(item)) {\n"
" value = PyLong_AsLong(item);\n"
" Py_DECREF(item);\n"
" if (value == -1 && PyErr_Occurred())\n"
" /* Integer too big to fit in a C long, bail out */\n"
" return -1;\n"
" total += value;\n"
" }\n"
" else {\n"
" Py_DECREF(item); /* Discard reference ownership */\n"
" }\n"
" }\n"
" return total;\n"
"}"
msgstr ""
msgid "Types"
msgstr ""
msgid ""
"There are few other data types that play a significant role in the Python/C "
"API; most are simple C types such as :c:expr:`int`, :c:expr:`long`, :c:expr:"
"`double` and :c:expr:`char*`. A few structure types are used to describe "
"static tables used to list the functions exported by a module or the data "
"attributes of a new object type, and another is used to describe the value "
"of a complex number. These will be discussed together with the functions "
"that use them."