导入模块
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PyObject* PyImport_ImportModule(const char *name)
    *Return value: New reference.*

   This is a simplified interface to "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.  A
   failing import of a module doesn't leave the module in
   "sys.modules".

   该函数总是使用绝对路径导入。

PyObject* PyImport_ImportModuleNoBlock(const char *name)
    *Return value: New reference.*

   该函数是 "PyImport_ImportModule()" 的一个被遗弃的别名。

   在 3.3 版更改: This function used to fail immediately when the
   import lock was held by another thread.  In Python 3.3 though, the
   locking scheme switched to per-module locks for most purposes, so
   this function's special behaviour isn't needed anymore.

PyObject* PyImport_ImportModuleEx(const char *name, PyObject *globals, PyObject *locals, PyObject *fromlist)
    *Return value: New reference.*

   Import a module.  This is best described by referring to the built-
   in Python function "__import__()".

   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 "__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
   "PyImport_ImportModule()".

PyObject* PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)
    *Return value: New reference.*

   Import a module.  This is best described by referring to the built-
   in Python function "__import__()", as the standard "__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 "__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.

   3.3 新版功能.

PyObject* PyImport_ImportModuleLevel(const char *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)
    *Return value: New reference.*

   Similar to "PyImport_ImportModuleLevelObject()", but the name is a
   UTF-8 encoded string instead of a Unicode object.

   在 3.3 版更改: Negative values for *level* are no longer accepted.

PyObject* PyImport_Import(PyObject *name)
    *Return value: New reference.*

   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 "__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.

   该函数总是使用绝对路径导入。

PyObject* PyImport_ReloadModule(PyObject *m)
    *Return value: New reference.*

   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).

PyObject* PyImport_AddModuleObject(PyObject *name)
    *Return value: Borrowed reference.*

   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.

   注解:

     This function does not load or import the module; if the module
     wasn't already loaded, you will get an empty module object. Use
     "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.

   3.3 新版功能.

PyObject* PyImport_AddModule(const char *name)
    *Return value: Borrowed reference.*

   Similar to "PyImport_AddModuleObject()", but the name is a UTF-8
   encoded string instead of a Unicode object.

PyObject* PyImport_ExecCodeModule(const char *name, PyObject *co)
    *Return value: New reference.*

   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 "compile()", load the module.  Return a new
   reference to the module object, or "NULL" with an exception set if
   an error occurred.  *name* is removed from "sys.modules" in error
   cases, even if *name* was already in "sys.modules" on entry to
   "PyImport_ExecCodeModule()".  Leaving incompletely initialized
   modules in "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.

   The module's "__spec__" and "__loader__" will be set, if not set
   already, with the appropriate values.  The spec's loader will be
   set to the module's "__loader__" (if set) and to an instance of
   "SourceFileLoader" otherwise.

   The module's "__file__" attribute will be set to the code object's
   "co_filename".  If applicable, "__cached__" will also be set.

   This function will reload the module if it was already imported.
   See "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.

   See also "PyImport_ExecCodeModuleEx()" and
   "PyImport_ExecCodeModuleWithPathnames()".

PyObject* PyImport_ExecCodeModuleEx(const char *name, PyObject *co, const char *pathname)
    *Return value: New reference.*

   Like "PyImport_ExecCodeModule()", but the "__file__" attribute of
   the module object is set to *pathname* if it is non-"NULL".

   参见 "PyImport_ExecCodeModuleWithPathnames()"。

PyObject* PyImport_ExecCodeModuleObject(PyObject *name, PyObject *co, PyObject *pathname, PyObject *cpathname)
    *Return value: New reference.*

   Like "PyImport_ExecCodeModuleEx()", but the "__cached__" attribute
   of the module object is set to *cpathname* if it is non-"NULL".  Of
   the three functions, this is the preferred one to use.

   3.3 新版功能.

PyObject* PyImport_ExecCodeModuleWithPathnames(const char *name, PyObject *co, const char *pathname, const char *cpathname)
    *Return value: New reference.*

   Like "PyImport_ExecCodeModuleObject()", but *name*, *pathname* and
   *cpathname* are UTF-8 encoded strings. Attempts are also made to
   figure out what the value for *pathname* should be from *cpathname*
   if the former is set to "NULL".

   3.2 新版功能.

   在 3.3 版更改: Uses "imp.source_from_cache()" in calculating the
   source path if only the bytecode path is provided.

long PyImport_GetMagicNumber()

   Return the magic number for Python bytecode files (a.k.a. ".pyc"
   file). The magic number should be present in the first four bytes
   of the bytecode file, in little-endian byte order. Returns "-1" on
   error.

   在 3.3 版更改: 失败时返回值 "-1"。

const char * PyImport_GetMagicTag()

   Return the magic tag string for **PEP 3147** format Python bytecode
   file names.  Keep in mind that the value at
   "sys.implementation.cache_tag" is authoritative and should be used
   instead of this function.

   3.2 新版功能.

PyObject* PyImport_GetModuleDict()
    *Return value: Borrowed reference.*

   Return the dictionary used for the module administration (a.k.a.
   "sys.modules").  Note that this is a per-interpreter variable.

PyObject* PyImport_GetModule(PyObject *name)
    *Return value: New reference.*

   Return the already imported module with the given name.  If the
   module has not been imported yet then returns "NULL" but does not
   set an error.  Returns "NULL" and sets an error if the lookup
   failed.

   3.7 新版功能.

PyObject* PyImport_GetImporter(PyObject *path)
    *Return value: New reference.*

   Return a finder object for a "sys.path"/"pkg.__path__" item *path*,
   possibly by fetching it from the "sys.path_importer_cache" dict.
   If it wasn't yet cached, traverse "sys.path_hooks" until a hook is
   found that can handle the path item.  Return "None" if no hook
   could; this tells our caller that the *path based finder* could not
   find a finder for this path item. Cache the result in
   "sys.path_importer_cache". Return a new reference to the finder
   object.

void _PyImport_Init()

   Initialize the import mechanism.  For internal use only.

void PyImport_Cleanup()

   Empty the module table.  For internal use only.

void _PyImport_Fini()

   Finalize the import mechanism.  For internal use only.

int PyImport_ImportFrozenModuleObject(PyObject *name)
    *Return value: New reference.*

   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 "PyImport_ImportModule()".  (Note the misnomer
   --- this function would reload the module if it was already
   imported.)

   3.3 新版功能.

   在 3.4 版更改: The "__file__" attribute is no longer set on the
   module.

int PyImport_ImportFrozenModule(const char *name)

   Similar to "PyImport_ImportFrozenModuleObject()", but the name is a
   UTF-8 encoded string instead of a Unicode object.

struct _frozen

   This is the structure type definition for frozen module
   descriptors, as generated by the **freeze** utility (see
   "Tools/freeze/" in the Python source distribution).  Its
   definition, found in "Include/import.h", is:

      struct _frozen {
          const char *name;
          const unsigned char *code;
          int size;
      };

const struct _frozen* PyImport_FrozenModules

   该指针被初始化为指向 "struct _frozen" 数组，以 "NULL" 或者 0 作为结
   束标记。当一个冻结模块被导入，首先要在这个表中搜索。第三方库可以以
   此来提供动态创建的冻结模块集合。

int PyImport_AppendInittab(const char *name, PyObject* (*initfunc)(void))

   Add a single module to the existing table of built-in modules.
   This is a convenience wrapper around "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 "Py_Initialize()".

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.
   The name is an ASCII encoded string.  Programs which embed Python
   may use an array of these structures in conjunction with
   "PyImport_ExtendInittab()" to provide additional built-in modules.
   The structure is defined in "Include/import.h" as:

      struct _inittab {
          const char *name;           /* ASCII encoded string */
          PyObject* (*initfunc)(void);
      };

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 "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 "Py_Initialize()".
