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diff --git a/Doc/c-api/import.rst b/Doc/c-api/import.rst new file mode 100644 index 0000000..907f531 --- /dev/null +++ b/Doc/c-api/import.rst @@ -0,0 +1,227 @@ +.. highlightlang:: c + +.. _importing: + +Importing Modules +================= + + +.. cfunction:: PyObject* PyImport_ImportModule(const char *name) + + .. index:: + single: package variable; __all__ + single: __all__ (package variable) + single: modules (in module sys) + + This is a simplified interface to :cfunc:`PyImport_ImportModuleEx` below, + leaving the *globals* and *locals* arguments set to *NULL* and *level* set + to 0. When the *name* + argument contains a dot (when it specifies a submodule of a package), the + *fromlist* argument is set to the list ``['*']`` so that the return value is the + named module rather than the top-level package containing it as would otherwise + be the case. (Unfortunately, this has an additional side effect when *name* in + fact specifies a subpackage instead of a submodule: the submodules specified in + the package's ``__all__`` variable are loaded.) Return a new reference to the + imported module, or *NULL* with an exception set on failure. Before Python 2.4, + the module may still be created in the failure case --- examine ``sys.modules`` + to find out. Starting with Python 2.4, a failing import of a module no longer + leaves the module in ``sys.modules``. + + +.. cfunction:: PyObject* PyImport_ImportModuleNoBlock(const char *name) + + This version of :cfunc:`PyImport_ImportModule` does not block. It's intended + to be used in C functions that import other modules to execute a function. + The import may block if another thread holds the import lock. The function + :cfunc:`PyImport_ImportModuleNoBlock` never blocks. It first tries to fetch + the module from sys.modules and falls back to :cfunc:`PyImport_ImportModule` + unless the lock is held, in which case the function will raise an + :exc:`ImportError`. + + +.. cfunction:: PyObject* PyImport_ImportModuleEx(char *name, PyObject *globals, PyObject *locals, PyObject *fromlist) + + .. index:: builtin: __import__ + + Import a module. This is best described by referring to the built-in Python + function :func:`__import__`, as the standard :func:`__import__` function calls + this function directly. + + The return value is a new reference to the imported module or top-level package, + or *NULL* with an exception set on failure (before Python 2.4, the module may + still be created in this case). Like for :func:`__import__`, the return value + when a submodule of a package was requested is normally the top-level package, + unless a non-empty *fromlist* was given. + + Failing imports remove incomplete module objects, like with + :cfunc:`PyImport_ImportModule`. + + +.. cfunction:: PyObject* PyImport_ImportModuleLevel(char *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level) + + Import a module. This is best described by referring to the built-in Python + function :func:`__import__`, as the standard :func:`__import__` function calls + this function directly. + + The return value is a new reference to the imported module or top-level package, + or *NULL* with an exception set on failure. Like for :func:`__import__`, + the return value when a submodule of a package was requested is normally the + top-level package, unless a non-empty *fromlist* was given. + + +.. cfunction:: PyObject* PyImport_Import(PyObject *name) + + This is a higher-level interface that calls the current "import hook + function" (with an explicit *level* of 0, meaning absolute import). It + invokes the :func:`__import__` function from the ``__builtins__`` of the + current globals. This means that the import is done using whatever import + hooks are installed in the current environment. + + +.. cfunction:: PyObject* PyImport_ReloadModule(PyObject *m) + + Reload a module. Return a new reference to the reloaded module, or *NULL* with + an exception set on failure (the module still exists in this case). + + +.. cfunction:: PyObject* PyImport_AddModule(const char *name) + + Return the module object corresponding to a module name. The *name* argument + may be of the form ``package.module``. First check the modules dictionary if + there's one there, and if not, create a new one and insert it in the modules + dictionary. Return *NULL* with an exception set on failure. + + .. note:: + + This function does not load or import the module; if the module wasn't already + loaded, you will get an empty module object. Use :cfunc:`PyImport_ImportModule` + or one of its variants to import a module. Package structures implied by a + dotted name for *name* are not created if not already present. + + +.. cfunction:: PyObject* PyImport_ExecCodeModule(char *name, PyObject *co) + + .. index:: builtin: compile + + Given a module name (possibly of the form ``package.module``) and a code object + read from a Python bytecode file or obtained from the built-in function + :func:`compile`, load the module. Return a new reference to the module object, + or *NULL* with an exception set if an error occurred. Before Python 2.4, the + module could still be created in error cases. Starting with Python 2.4, *name* + is removed from :attr:`sys.modules` in error cases, and even if *name* was already + in :attr:`sys.modules` on entry to :cfunc:`PyImport_ExecCodeModule`. Leaving + incompletely initialized modules in :attr:`sys.modules` is dangerous, as imports of + such modules have no way to know that the module object is an unknown (and + probably damaged with respect to the module author's intents) state. + + This function will reload the module if it was already imported. See + :cfunc:`PyImport_ReloadModule` for the intended way to reload a module. + + If *name* points to a dotted name of the form ``package.module``, any package + structures not already created will still not be created. + + +.. cfunction:: long PyImport_GetMagicNumber() + + Return the magic number for Python bytecode files (a.k.a. :file:`.pyc` and + :file:`.pyo` files). The magic number should be present in the first four bytes + of the bytecode file, in little-endian byte order. + + +.. cfunction:: PyObject* PyImport_GetModuleDict() + + Return the dictionary used for the module administration (a.k.a. + ``sys.modules``). Note that this is a per-interpreter variable. + + +.. cfunction:: void _PyImport_Init() + + Initialize the import mechanism. For internal use only. + + +.. cfunction:: void PyImport_Cleanup() + + Empty the module table. For internal use only. + + +.. cfunction:: void _PyImport_Fini() + + Finalize the import mechanism. For internal use only. + + +.. cfunction:: PyObject* _PyImport_FindExtension(char *, char *) + + For internal use only. + + +.. cfunction:: PyObject* _PyImport_FixupExtension(char *, char *) + + For internal use only. + + +.. cfunction:: int PyImport_ImportFrozenModule(char *name) + + Load a frozen module named *name*. Return ``1`` for success, ``0`` if the + module is not found, and ``-1`` with an exception set if the initialization + failed. To access the imported module on a successful load, use + :cfunc:`PyImport_ImportModule`. (Note the misnomer --- this function would + reload the module if it was already imported.) + + +.. ctype:: struct _frozen + + .. index:: single: freeze utility + + This is the structure type definition for frozen module descriptors, as + generated by the :program:`freeze` utility (see :file:`Tools/freeze/` in the + Python source distribution). Its definition, found in :file:`Include/import.h`, + is:: + + struct _frozen { + char *name; + unsigned char *code; + int size; + }; + + +.. cvar:: struct _frozen* PyImport_FrozenModules + + This pointer is initialized to point to an array of :ctype:`struct _frozen` + records, terminated by one whose members are all *NULL* or zero. When a frozen + module is imported, it is searched in this table. Third-party code could play + tricks with this to provide a dynamically created collection of frozen modules. + + +.. cfunction:: int PyImport_AppendInittab(char *name, void (*initfunc)(void)) + + Add a single module to the existing table of built-in modules. This is a + convenience wrapper around :cfunc:`PyImport_ExtendInittab`, returning ``-1`` if + the table could not be extended. The new module can be imported by the name + *name*, and uses the function *initfunc* as the initialization function called + on the first attempted import. This should be called before + :cfunc:`Py_Initialize`. + + +.. ctype:: struct _inittab + + Structure describing a single entry in the list of built-in modules. Each of + these structures gives the name and initialization function for a module built + into the interpreter. Programs which embed Python may use an array of these + structures in conjunction with :cfunc:`PyImport_ExtendInittab` to provide + additional built-in modules. The structure is defined in + :file:`Include/import.h` as:: + + struct _inittab { + char *name; + void (*initfunc)(void); + }; + + +.. cfunction:: int PyImport_ExtendInittab(struct _inittab *newtab) + + Add a collection of modules to the table of built-in modules. The *newtab* + array must end with a sentinel entry which contains *NULL* for the :attr:`name` + field; failure to provide the sentinel value can result in a memory fault. + Returns ``0`` on success or ``-1`` if insufficient memory could be allocated to + extend the internal table. In the event of failure, no modules are added to the + internal table. This should be called before :cfunc:`Py_Initialize`. |