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<title>5.3 Importing Modules </title>
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<H1><A NAME="SECTION007300000000000000000"></A><A NAME="importing"></A>
<BR>
5.3 Importing Modules
</H1>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-170' xml:id='l2h-170' class="cfunction">PyImport_ImportModule</tt></b>(</nobr></td><td>char *<var>name</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">New reference.</span>
</div>
  This is a simplified interface to
  <tt class="cfunction">PyImport_ImportModuleEx()</tt> below, leaving the
  <var>globals</var> and <var>locals</var> arguments set to <tt class="constant">NULL</tt>.  When the
  <var>name</var> argument contains a dot (when it specifies a submodule of
  a package), the <var>fromlist</var> argument is set to the list
  <code>['*']</code> 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
  <var>name</var> in fact specifies a subpackage instead of a submodule:
  the submodules specified in the package's <code>__all__</code> variable
  are <a id='l2h-196' xml:id='l2h-196'></a>
  <a id='l2h-172' xml:id='l2h-172'></a>loaded.)  Return
  a new reference to the imported module, or <tt class="constant">NULL</tt> with an exception
  set on failure.  Before Python 2.4, the module may still be created in
  the failure case -- examine <code>sys.modules</code> to find out.  Starting
  with Python 2.4, a failing import of a module no longer leaves the
  module in <code>sys.modules</code>.

<span class="versionnote">Changed in version 2.4:
failing imports remove incomplete module objects.</span>

  <a id='l2h-174' xml:id='l2h-174'></a></dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-175' xml:id='l2h-175' class="cfunction">PyImport_ImportModuleEx</tt></b>(</nobr></td><td>char *<var>name</var>,
                       PyObject *<var>globals</var>, PyObject *<var>locals</var>, PyObject *<var>fromlist</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">New reference.</span>
</div>
  Import a module.  This is best described by referring to the
  built-in Python function
  <tt class="function">__import__()</tt><a id='l2h-176' xml:id='l2h-176'></a>, as the standard
  <tt class="function">__import__()</tt> function calls this function directly.

<P>
The return value is a new reference to the imported module or
  top-level package, or <tt class="constant">NULL</tt> with an exception set on failure (before
  Python 2.4, the
  module may still be created in this case).  Like for
  <tt class="function">__import__()</tt>, the return value when a submodule of a
  package was requested is normally the top-level package, unless a
  non-empty <var>fromlist</var> was given.

<span class="versionnote">Changed in version 2.4:
failing imports remove incomplete module objects.</span>

</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-177' xml:id='l2h-177' class="cfunction">PyImport_Import</tt></b>(</nobr></td><td>PyObject *<var>name</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">New reference.</span>
</div>
  This is a higher-level interface that calls the current ``import
  hook function''.  It invokes the <tt class="function">__import__()</tt> function
  from the <code>__builtins__</code> of the current globals.  This means
  that the import is done using whatever import hooks are installed in
  the current environment, e.g. by <tt class="module">rexec</tt><a id='l2h-197' xml:id='l2h-197'></a>
  or <tt class="module">ihooks</tt><a id='l2h-198' xml:id='l2h-198'></a>.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-178' xml:id='l2h-178' class="cfunction">PyImport_ReloadModule</tt></b>(</nobr></td><td>PyObject *<var>m</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">New reference.</span>
</div>
  Reload a module.  This is best described by referring to the
  built-in Python function <tt class="function">reload()</tt><a id='l2h-179' xml:id='l2h-179'></a>, as
  the standard <tt class="function">reload()</tt> function calls this function
  directly.  Return a new reference to the reloaded module, or <tt class="constant">NULL</tt>
  with an exception set on failure (the module still exists in this
  case).
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-180' xml:id='l2h-180' class="cfunction">PyImport_AddModule</tt></b>(</nobr></td><td>char *<var>name</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">Borrowed reference.</span>
</div>
  Return the module object corresponding to a module name.  The
  <var>name</var> argument may be of the form <code>package.module</code>.
  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 <tt class="constant">NULL</tt> with an exception set on failure.
  <span class="note"><b class="label">Note:</b>
This function does not load or import the module; if the
  module wasn't already loaded, you will get an empty module object.
  Use <tt class="cfunction">PyImport_ImportModule()</tt> or one of its variants to
  import a module.  Package structures implied by a dotted name for
  <var>name</var> are not created if not already present.</span>
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-181' xml:id='l2h-181' class="cfunction">PyImport_ExecCodeModule</tt></b>(</nobr></td><td>char *<var>name</var>, PyObject *<var>co</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">New reference.</span>
</div>
  Given a module name (possibly of the form <code>package.module</code>) and
  a code object read from a Python bytecode file or obtained from the
  built-in function <tt class="function">compile()</tt><a id='l2h-182' xml:id='l2h-182'></a>, load
  the module.  Return a new reference to the module object, or <tt class="constant">NULL</tt>
  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,
  <var>name</var> is removed from <code>sys.modules</code> in error cases, and even
  if <var>name</var> was already in <code>sys.modules</code> on entry to
  <tt class="cfunction">PyImport_ExecCodeModule()</tt>.  Leaving incompletely initialized
  modules in <code>sys.modules</code> 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.

<P>
This function will reload the module if it was already imported.  See
  <tt class="cfunction">PyImport_ReloadModule()</tt> for the intended way to reload a
  module.

<P>
If <var>name</var> points to a dotted name of the
  form <code>package.module</code>, any package structures not already
  created will still not be created.

<P>

<span class="versionnote">Changed in version 2.4:
<var>name</var> is removed from <code>sys.modules</code> in error cases.</span>

<P>
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>long&nbsp;<b><tt id='l2h-183' xml:id='l2h-183' class="cfunction">PyImport_GetMagicNumber</tt></b>(</nobr></td><td>)</td></tr></table></dt>
<dd>
  Return the magic number for Python bytecode files
  (a.k.a. <span class="file">.pyc</span> and <span class="file">.pyo</span> files).  The magic number should
  be present in the first four bytes of the bytecode file, in
  little-endian byte order.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-184' xml:id='l2h-184' class="cfunction">PyImport_GetModuleDict</tt></b>(</nobr></td><td>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">Borrowed reference.</span>
</div>
  Return the dictionary used for the module administration
  (a.k.a. <code>sys.modules</code>).  Note that this is a per-interpreter
  variable.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void&nbsp;<b><tt id='l2h-185' xml:id='l2h-185' class="cfunction">_PyImport_Init</tt></b>(</nobr></td><td>)</td></tr></table></dt>
<dd>
  Initialize the import mechanism.  For internal use only.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void&nbsp;<b><tt id='l2h-186' xml:id='l2h-186' class="cfunction">PyImport_Cleanup</tt></b>(</nobr></td><td>)</td></tr></table></dt>
<dd>
  Empty the module table.  For internal use only.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void&nbsp;<b><tt id='l2h-187' xml:id='l2h-187' class="cfunction">_PyImport_Fini</tt></b>(</nobr></td><td>)</td></tr></table></dt>
<dd>
  Finalize the import mechanism.  For internal use only.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-188' xml:id='l2h-188' class="cfunction">_PyImport_FindExtension</tt></b>(</nobr></td><td>char *, char *)</td></tr></table></dt>
<dd>
<div class="refcount-info">
  <span class="label">Return value:</span>
  <span class="value">Borrowed reference.</span>
</div>
  For internal use only.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject*&nbsp;<b><tt id='l2h-189' xml:id='l2h-189' class="cfunction">_PyImport_FixupExtension</tt></b>(</nobr></td><td>char *, char *)</td></tr></table></dt>
<dd>
  For internal use only.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int&nbsp;<b><tt id='l2h-190' xml:id='l2h-190' class="cfunction">PyImport_ImportFrozenModule</tt></b>(</nobr></td><td>char *<var>name</var>)</td></tr></table></dt>
<dd>
  Load a frozen module named <var>name</var>.  Return <code>1</code> for success,
  <code>0</code> if the module is not found, and <code>-1</code> with an exception
  set if the initialization failed.  To access the imported module on
  a successful load, use <tt class="cfunction">PyImport_ImportModule()</tt>.  (Note
  the misnomer -- this function would reload the module if it was
  already imported.)
</dd></dl>

<P>
<dl><dt><b><tt class="ctype"><a id='l2h-191' xml:id='l2h-191'>struct _frozen</a></tt></b></dt>
<dd>
  This is the structure type definition for frozen module descriptors,
  as generated by the <b class="program">freeze</b><a id='l2h-199' xml:id='l2h-199'></a> utility
  (see <span class="file">Tools/freeze/</span> in the Python source distribution).  Its
  definition, found in <span class="file">Include/import.h</span>, is:

<P>
<div class="verbatim"><pre>
struct _frozen {
    char *name;
    unsigned char *code;
    int size;
};
</pre></div>
</dl>

<P>
<dl><dt>struct _frozen* <b><tt id='l2h-192' xml:id='l2h-192' class="cdata">PyImport_FrozenModules</tt></b></dt>
<dd>
  This pointer is initialized to point to an array of <tt class="ctype">struct
  _frozen</tt> records, terminated by one whose members are all <tt class="constant">NULL</tt> 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.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int&nbsp;<b><tt id='l2h-193' xml:id='l2h-193' class="cfunction">PyImport_AppendInittab</tt></b>(</nobr></td><td>char *<var>name</var>,
                                               void (*initfunc)(void))</td></tr></table></dt>
<dd>
  Add a single module to the existing table of built-in modules.  This
  is a convenience wrapper around
  <tt class="cfunction">PyImport_ExtendInittab()</tt>, returning <code>-1</code> if the
  table could not be extended.  The new module can be imported by the
  name <var>name</var>, and uses the function <var>initfunc</var> as the
  initialization function called on the first attempted import.  This
  should be called before <tt class="cfunction">Py_Initialize()</tt>.
</dd></dl>

<P>
<dl><dt><b><tt class="ctype"><a id='l2h-194' xml:id='l2h-194'>struct _inittab</a></tt></b></dt>
<dd>
  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 <tt class="cfunction">PyImport_ExtendInittab()</tt> to provide additional
  built-in modules.  The structure is defined in
  <span class="file">Include/import.h</span> as:

<P>
<div class="verbatim"><pre>
struct _inittab {
    char *name;
    void (*initfunc)(void);
};
</pre></div>
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int&nbsp;<b><tt id='l2h-195' xml:id='l2h-195' class="cfunction">PyImport_ExtendInittab</tt></b>(</nobr></td><td>struct _inittab *<var>newtab</var>)</td></tr></table></dt>
<dd>
  Add a collection of modules to the table of built-in modules.  The
  <var>newtab</var> array must end with a sentinel entry which contains
  <tt class="constant">NULL</tt> for the <tt class="member">name</tt> field; failure to provide the sentinel
  value can result in a memory fault.  Returns <code>0</code> on success or
  <code>-1</code> 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
  <tt class="cfunction">Py_Initialize()</tt>.
</dd></dl>

<P>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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