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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* <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* <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* <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* <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* <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* <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 <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* <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 <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 <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 <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* <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* <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 <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 <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 <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>
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<span class="release-info">Release 2.4.3, documentation updated on 29 March 2006.</span>
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