<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>29.1. imp — Access the import internals — Python v3.1.1 documentation</title>
<link rel="stylesheet" href="../_static/default.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT: '../',
VERSION: '3.1.1',
COLLAPSE_MODINDEX: false,
FILE_SUFFIX: '.html',
HAS_SOURCE: true
};
</script>
<script type="text/javascript" src="../_static/jquery.js"></script>
<script type="text/javascript" src="../_static/doctools.js"></script>
<link rel="search" type="application/opensearchdescription+xml"
title="Search within Python v3.1.1 documentation"
href="../_static/opensearch.xml"/>
<link rel="author" title="About these documents" href="../about.html" />
<link rel="copyright" title="Copyright" href="../copyright.html" />
<link rel="top" title="Python v3.1.1 documentation" href="../index.html" />
<link rel="up" title="29. Importing Modules" href="modules.html" />
<link rel="next" title="29.2. zipimport — Import modules from Zip archives" href="zipimport.html" />
<link rel="prev" title="29. Importing Modules" href="modules.html" />
<link rel="shortcut icon" type="image/png" href="../_static/py.png" />
</head>
<body>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../genindex.html" title="General Index"
accesskey="I">index</a></li>
<li class="right" >
<a href="../modindex.html" title="Global Module Index"
accesskey="M">modules</a> |</li>
<li class="right" >
<a href="zipimport.html" title="29.2. zipimport — Import modules from Zip archives"
accesskey="N">next</a> |</li>
<li class="right" >
<a href="modules.html" title="29. Importing Modules"
accesskey="P">previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="../index.html">Python v3.1.1 documentation</a> »</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="modules.html" accesskey="U">29. Importing Modules</a> »</li>
</ul>
</div>
<div class="document">
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body">
<div class="section" id="module-imp">
<h1>29.1. <tt class="xref docutils literal"><span class="pre">imp</span></tt> — Access the <a class="reference external" href="../reference/simple_stmts.html#import"><tt class="xref docutils literal"><span class="pre">import</span></tt></a> internals<a class="headerlink" href="#module-imp" title="Permalink to this headline">¶</a></h1>
<p id="index-349">This module provides an interface to the mechanisms used to implement the
<a class="reference external" href="../reference/simple_stmts.html#import"><tt class="xref docutils literal"><span class="pre">import</span></tt></a> statement. It defines the following constants and functions:</p>
<dl class="function">
<dt id="imp.get_magic">
<tt class="descclassname">imp.</tt><tt class="descname">get_magic</tt><big>(</big><big>)</big><a class="headerlink" href="#imp.get_magic" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-350">Return the magic string value used to recognize byte-compiled code files
(<tt class="docutils literal"><span class="pre">.pyc</span></tt> files). (This value may be different for each Python version.)</p>
</dd></dl>
<dl class="function">
<dt id="imp.get_suffixes">
<tt class="descclassname">imp.</tt><tt class="descname">get_suffixes</tt><big>(</big><big>)</big><a class="headerlink" href="#imp.get_suffixes" title="Permalink to this definition">¶</a></dt>
<dd>Return a list of 3-element tuples, each describing a particular type of
module. Each triple has the form <tt class="docutils literal"><span class="pre">(suffix,</span> <span class="pre">mode,</span> <span class="pre">type)</span></tt>, where <em>suffix</em> is
a string to be appended to the module name to form the filename to search
for, <em>mode</em> is the mode string to pass to the built-in <a title="open" class="reference external" href="functions.html#open"><tt class="xref docutils literal"><span class="pre">open()</span></tt></a> function
to open the file (this can be <tt class="docutils literal"><span class="pre">'r'</span></tt> for text files or <tt class="docutils literal"><span class="pre">'rb'</span></tt> for binary
files), and <em>type</em> is the file type, which has one of the values
<a title="imp.PY_SOURCE" class="reference internal" href="#imp.PY_SOURCE"><tt class="xref docutils literal"><span class="pre">PY_SOURCE</span></tt></a>, <a title="imp.PY_COMPILED" class="reference internal" href="#imp.PY_COMPILED"><tt class="xref docutils literal"><span class="pre">PY_COMPILED</span></tt></a>, or <a title="imp.C_EXTENSION" class="reference internal" href="#imp.C_EXTENSION"><tt class="xref docutils literal"><span class="pre">C_EXTENSION</span></tt></a>, described
below.</dd></dl>
<dl class="function">
<dt id="imp.find_module">
<tt class="descclassname">imp.</tt><tt class="descname">find_module</tt><big>(</big><em>name</em><span class="optional">[</span>, <em>path</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#imp.find_module" title="Permalink to this definition">¶</a></dt>
<dd><p>Try to find the module <em>name</em>. If <em>path</em> is omitted or <tt class="xref docutils literal"><span class="pre">None</span></tt>, the list of
directory names given by <tt class="docutils literal"><span class="pre">sys.path</span></tt> is searched, but first a few special
places are searched: the function tries to find a built-in module with the
given name (<a title="imp.C_BUILTIN" class="reference internal" href="#imp.C_BUILTIN"><tt class="xref docutils literal"><span class="pre">C_BUILTIN</span></tt></a>), then a frozen module (<a title="imp.PY_FROZEN" class="reference internal" href="#imp.PY_FROZEN"><tt class="xref docutils literal"><span class="pre">PY_FROZEN</span></tt></a>),
and on some systems some other places are looked in as well (on Windows, it
looks in the registry which may point to a specific file).</p>
<p>Otherwise, <em>path</em> must be a list of directory names; each directory is
searched for files with any of the suffixes returned by <a title="imp.get_suffixes" class="reference internal" href="#imp.get_suffixes"><tt class="xref docutils literal"><span class="pre">get_suffixes()</span></tt></a>
above. Invalid names in the list are silently ignored (but all list items
must be strings).</p>
<p>If search is successful, the return value is a 3-element tuple <tt class="docutils literal"><span class="pre">(file,</span>
<span class="pre">pathname,</span> <span class="pre">description)</span></tt>:</p>
<p><em>file</em> is an open file object positioned at the beginning, <em>pathname</em> is the
pathname of the file found, and <em>description</em> is a 3-element tuple as
contained in the list returned by <a title="imp.get_suffixes" class="reference internal" href="#imp.get_suffixes"><tt class="xref docutils literal"><span class="pre">get_suffixes()</span></tt></a> describing the kind of
module found.</p>
<p>If the module does not live in a file, the returned <em>file</em> is <tt class="xref docutils literal"><span class="pre">None</span></tt>,
<em>pathname</em> is the empty string, and the <em>description</em> tuple contains empty
strings for its suffix and mode; the module type is indicated as given in
parentheses above. If the search is unsuccessful, <a title="exceptions.ImportError" class="reference external" href="exceptions.html#exceptions.ImportError"><tt class="xref docutils literal"><span class="pre">ImportError</span></tt></a> is
raised. Other exceptions indicate problems with the arguments or
environment.</p>
<p>If the module is a package, <em>file</em> is <tt class="xref docutils literal"><span class="pre">None</span></tt>, <em>pathname</em> is the package
path and the last item in the <em>description</em> tuple is <a title="imp.PKG_DIRECTORY" class="reference internal" href="#imp.PKG_DIRECTORY"><tt class="xref docutils literal"><span class="pre">PKG_DIRECTORY</span></tt></a>.</p>
<p>This function does not handle hierarchical module names (names containing
dots). In order to find <em>P</em>.*M*, that is, submodule <em>M</em> of package <em>P</em>, use
<a title="imp.find_module" class="reference internal" href="#imp.find_module"><tt class="xref docutils literal"><span class="pre">find_module()</span></tt></a> and <a title="imp.load_module" class="reference internal" href="#imp.load_module"><tt class="xref docutils literal"><span class="pre">load_module()</span></tt></a> to find and load package <em>P</em>, and
then use <a title="imp.find_module" class="reference internal" href="#imp.find_module"><tt class="xref docutils literal"><span class="pre">find_module()</span></tt></a> with the <em>path</em> argument set to <tt class="docutils literal"><span class="pre">P.__path__</span></tt>.
When <em>P</em> itself has a dotted name, apply this recipe recursively.</p>
</dd></dl>
<dl class="function">
<dt id="imp.load_module">
<tt class="descclassname">imp.</tt><tt class="descname">load_module</tt><big>(</big><em>name</em>, <em>file</em>, <em>pathname</em>, <em>description</em><big>)</big><a class="headerlink" href="#imp.load_module" title="Permalink to this definition">¶</a></dt>
<dd><p>Load a module that was previously found by <a title="imp.find_module" class="reference internal" href="#imp.find_module"><tt class="xref docutils literal"><span class="pre">find_module()</span></tt></a> (or by an
otherwise conducted search yielding compatible results). This function does
more than importing the module: if the module was already imported, it will
reload the module! The <em>name</em> argument indicates the full
module name (including the package name, if this is a submodule of a
package). The <em>file</em> argument is an open file, and <em>pathname</em> is the
corresponding file name; these can be <tt class="xref docutils literal"><span class="pre">None</span></tt> and <tt class="docutils literal"><span class="pre">''</span></tt>, respectively, when
the module is a package or not being loaded from a file. The <em>description</em>
argument is a tuple, as would be returned by <a title="imp.get_suffixes" class="reference internal" href="#imp.get_suffixes"><tt class="xref docutils literal"><span class="pre">get_suffixes()</span></tt></a>, describing
what kind of module must be loaded.</p>
<p>If the load is successful, the return value is the module object; otherwise,
an exception (usually <a title="exceptions.ImportError" class="reference external" href="exceptions.html#exceptions.ImportError"><tt class="xref docutils literal"><span class="pre">ImportError</span></tt></a>) is raised.</p>
<p><strong>Important:</strong> the caller is responsible for closing the <em>file</em> argument, if
it was not <tt class="xref docutils literal"><span class="pre">None</span></tt>, even when an exception is raised. This is best done
using a <a class="reference external" href="../reference/compound_stmts.html#try"><tt class="xref docutils literal"><span class="pre">try</span></tt></a> ... <a class="reference external" href="../reference/compound_stmts.html#finally"><tt class="xref docutils literal"><span class="pre">finally</span></tt></a> statement.</p>
</dd></dl>
<dl class="function">
<dt id="imp.new_module">
<tt class="descclassname">imp.</tt><tt class="descname">new_module</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#imp.new_module" title="Permalink to this definition">¶</a></dt>
<dd>Return a new empty module object called <em>name</em>. This object is <em>not</em> inserted
in <tt class="docutils literal"><span class="pre">sys.modules</span></tt>.</dd></dl>
<dl class="function">
<dt id="imp.lock_held">
<tt class="descclassname">imp.</tt><tt class="descname">lock_held</tt><big>(</big><big>)</big><a class="headerlink" href="#imp.lock_held" title="Permalink to this definition">¶</a></dt>
<dd><p>Return <tt class="xref docutils literal"><span class="pre">True</span></tt> if the import lock is currently held, else <tt class="xref docutils literal"><span class="pre">False</span></tt>. On
platforms without threads, always return <tt class="xref docutils literal"><span class="pre">False</span></tt>.</p>
<p>On platforms with threads, a thread executing an import holds an internal lock
until the import is complete. This lock blocks other threads from doing an
import until the original import completes, which in turn prevents other threads
from seeing incomplete module objects constructed by the original thread while
in the process of completing its import (and the imports, if any, triggered by
that).</p>
</dd></dl>
<dl class="function">
<dt id="imp.acquire_lock">
<tt class="descclassname">imp.</tt><tt class="descname">acquire_lock</tt><big>(</big><big>)</big><a class="headerlink" href="#imp.acquire_lock" title="Permalink to this definition">¶</a></dt>
<dd><p>Acquire the interpreter’s import lock for the current thread. This lock should
be used by import hooks to ensure thread-safety when importing modules. On
platforms without threads, this function does nothing.</p>
<p>Once a thread has acquired the import lock, the same thread may acquire it
again without blocking; the thread must release it once for each time it has
acquired it.</p>
<p>On platforms without threads, this function does nothing.</p>
</dd></dl>
<dl class="function">
<dt id="imp.release_lock">
<tt class="descclassname">imp.</tt><tt class="descname">release_lock</tt><big>(</big><big>)</big><a class="headerlink" href="#imp.release_lock" title="Permalink to this definition">¶</a></dt>
<dd>Release the interpreter’s import lock. On platforms without threads, this
function does nothing.</dd></dl>
<dl class="function">
<dt id="imp.reload">
<tt class="descclassname">imp.</tt><tt class="descname">reload</tt><big>(</big><em>module</em><big>)</big><a class="headerlink" href="#imp.reload" title="Permalink to this definition">¶</a></dt>
<dd><p>Reload a previously imported <em>module</em>. The argument must be a module object, so
it must have been successfully imported before. This is useful if you have
edited the module source file using an external editor and want to try out the
new version without leaving the Python interpreter. The return value is the
module object (the same as the <em>module</em> argument).</p>
<p>When <tt class="docutils literal"><span class="pre">reload(module)</span></tt> is executed:</p>
<ul class="simple">
<li>Python modules’ code is recompiled and the module-level code reexecuted,
defining a new set of objects which are bound to names in the module’s
dictionary. The <tt class="docutils literal"><span class="pre">init</span></tt> function of extension modules is not called a second
time.</li>
<li>As with all other objects in Python the old objects are only reclaimed after
their reference counts drop to zero.</li>
<li>The names in the module namespace are updated to point to any new or changed
objects.</li>
<li>Other references to the old objects (such as names external to the module) are
not rebound to refer to the new objects and must be updated in each namespace
where they occur if that is desired.</li>
</ul>
<p>There are a number of other caveats:</p>
<p>If a module is syntactically correct but its initialization fails, the first
<a class="reference external" href="../reference/simple_stmts.html#import"><tt class="xref docutils literal"><span class="pre">import</span></tt></a> statement for it does not bind its name locally, but does
store a (partially initialized) module object in <tt class="docutils literal"><span class="pre">sys.modules</span></tt>. To reload the
module you must first <a class="reference external" href="../reference/simple_stmts.html#import"><tt class="xref docutils literal"><span class="pre">import</span></tt></a> it again (this will bind the name to the
partially initialized module object) before you can <a title="imp.reload" class="reference internal" href="#imp.reload"><tt class="xref docutils literal"><span class="pre">reload()</span></tt></a> it.</p>
<p>When a module is reloaded, its dictionary (containing the module’s global
variables) is retained. Redefinitions of names will override the old
definitions, so this is generally not a problem. If the new version of a module
does not define a name that was defined by the old version, the old definition
remains. This feature can be used to the module’s advantage if it maintains a
global table or cache of objects — with a <a class="reference external" href="../reference/compound_stmts.html#try"><tt class="xref docutils literal"><span class="pre">try</span></tt></a> statement it can test
for the table’s presence and skip its initialization if desired:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="k">try</span><span class="p">:</span>
<span class="n">cache</span>
<span class="k">except</span> <span class="ne">NameError</span><span class="p">:</span>
<span class="n">cache</span> <span class="o">=</span> <span class="p">{}</span>
</pre></div>
</div>
<p>It is legal though generally not very useful to reload built-in or dynamically
loaded modules, except for <a title="Access system-specific parameters and functions." class="reference external" href="sys.html#module-sys"><tt class="xref docutils literal"><span class="pre">sys</span></tt></a>, <a title="The environment where the top-level script is run." class="reference external" href="__main__.html#module-__main__"><tt class="xref docutils literal"><span class="pre">__main__</span></tt></a> and <tt class="xref docutils literal"><span class="pre">__builtin__</span></tt>.
In many cases, however, extension modules are not designed to be initialized
more than once, and may fail in arbitrary ways when reloaded.</p>
<p>If a module imports objects from another module using <a class="reference external" href="../reference/simple_stmts.html#from"><tt class="xref docutils literal"><span class="pre">from</span></tt></a> ...
<a class="reference external" href="../reference/simple_stmts.html#import"><tt class="xref docutils literal"><span class="pre">import</span></tt></a> ..., calling <a title="imp.reload" class="reference internal" href="#imp.reload"><tt class="xref docutils literal"><span class="pre">reload()</span></tt></a> for the other module does not
redefine the objects imported from it — one way around this is to re-execute
the <a class="reference external" href="../reference/simple_stmts.html#from"><tt class="xref docutils literal"><span class="pre">from</span></tt></a> statement, another is to use <a class="reference external" href="../reference/simple_stmts.html#import"><tt class="xref docutils literal"><span class="pre">import</span></tt></a> and qualified
names (<em>module</em>.*name*) instead.</p>
<p>If a module instantiates instances of a class, reloading the module that defines
the class does not affect the method definitions of the instances — they
continue to use the old class definition. The same is true for derived classes.</p>
</dd></dl>
<dl class="function">
<dt>
<tt class="descclassname">imp.</tt><tt class="descname">acquire_lock</tt><big>(</big><big>)</big></dt>
<dd>Acquires the interpreter’s import lock for the current thread. This lock should
be used by import hooks to ensure thread-safety when importing modules. On
platforms without threads, this function does nothing.</dd></dl>
<dl class="function">
<dt>
<tt class="descclassname">imp.</tt><tt class="descname">release_lock</tt><big>(</big><big>)</big></dt>
<dd>Release the interpreter’s import lock. On platforms without threads, this
function does nothing.</dd></dl>
<p>The following constants with integer values, defined in this module, are used to
indicate the search result of <a title="imp.find_module" class="reference internal" href="#imp.find_module"><tt class="xref docutils literal"><span class="pre">find_module()</span></tt></a>.</p>
<dl class="data">
<dt id="imp.PY_SOURCE">
<tt class="descclassname">imp.</tt><tt class="descname">PY_SOURCE</tt><a class="headerlink" href="#imp.PY_SOURCE" title="Permalink to this definition">¶</a></dt>
<dd>The module was found as a source file.</dd></dl>
<dl class="data">
<dt id="imp.PY_COMPILED">
<tt class="descclassname">imp.</tt><tt class="descname">PY_COMPILED</tt><a class="headerlink" href="#imp.PY_COMPILED" title="Permalink to this definition">¶</a></dt>
<dd>The module was found as a compiled code object file.</dd></dl>
<dl class="data">
<dt id="imp.C_EXTENSION">
<tt class="descclassname">imp.</tt><tt class="descname">C_EXTENSION</tt><a class="headerlink" href="#imp.C_EXTENSION" title="Permalink to this definition">¶</a></dt>
<dd>The module was found as dynamically loadable shared library.</dd></dl>
<dl class="data">
<dt id="imp.PKG_DIRECTORY">
<tt class="descclassname">imp.</tt><tt class="descname">PKG_DIRECTORY</tt><a class="headerlink" href="#imp.PKG_DIRECTORY" title="Permalink to this definition">¶</a></dt>
<dd>The module was found as a package directory.</dd></dl>
<dl class="data">
<dt id="imp.C_BUILTIN">
<tt class="descclassname">imp.</tt><tt class="descname">C_BUILTIN</tt><a class="headerlink" href="#imp.C_BUILTIN" title="Permalink to this definition">¶</a></dt>
<dd>The module was found as a built-in module.</dd></dl>
<dl class="data">
<dt id="imp.PY_FROZEN">
<tt class="descclassname">imp.</tt><tt class="descname">PY_FROZEN</tt><a class="headerlink" href="#imp.PY_FROZEN" title="Permalink to this definition">¶</a></dt>
<dd>The module was found as a frozen module (see <a title="imp.init_frozen" class="reference internal" href="#imp.init_frozen"><tt class="xref docutils literal"><span class="pre">init_frozen()</span></tt></a>).</dd></dl>
<p>The following constant and functions are obsolete; their functionality is
available through <a title="imp.find_module" class="reference internal" href="#imp.find_module"><tt class="xref docutils literal"><span class="pre">find_module()</span></tt></a> or <a title="imp.load_module" class="reference internal" href="#imp.load_module"><tt class="xref docutils literal"><span class="pre">load_module()</span></tt></a>. They are kept
around for backward compatibility:</p>
<dl class="data">
<dt id="imp.SEARCH_ERROR">
<tt class="descclassname">imp.</tt><tt class="descname">SEARCH_ERROR</tt><a class="headerlink" href="#imp.SEARCH_ERROR" title="Permalink to this definition">¶</a></dt>
<dd>Unused.</dd></dl>
<dl class="function">
<dt id="imp.init_builtin">
<tt class="descclassname">imp.</tt><tt class="descname">init_builtin</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#imp.init_builtin" title="Permalink to this definition">¶</a></dt>
<dd>Initialize the built-in module called <em>name</em> and return its module object along
with storing it in <tt class="docutils literal"><span class="pre">sys.modules</span></tt>. If the module was already initialized, it
will be initialized <em>again</em>. Re-initialization involves the copying of the
built-in module’s <tt class="docutils literal"><span class="pre">__dict__</span></tt> from the cached module over the module’s entry in
<tt class="docutils literal"><span class="pre">sys.modules</span></tt>. If there is no built-in module called <em>name</em>, <tt class="xref docutils literal"><span class="pre">None</span></tt> is
returned.</dd></dl>
<dl class="function">
<dt id="imp.init_frozen">
<tt class="descclassname">imp.</tt><tt class="descname">init_frozen</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#imp.init_frozen" title="Permalink to this definition">¶</a></dt>
<dd>Initialize the frozen module called <em>name</em> and return its module object. If
the module was already initialized, it will be initialized <em>again</em>. If there
is no frozen module called <em>name</em>, <tt class="xref docutils literal"><span class="pre">None</span></tt> is returned. (Frozen modules are
modules written in Python whose compiled byte-code object is incorporated
into a custom-built Python interpreter by Python’s <strong>freeze</strong>
utility. See <tt class="docutils literal"><span class="pre">Tools/freeze/</span></tt> for now.)</dd></dl>
<dl class="function">
<dt id="imp.is_builtin">
<tt class="descclassname">imp.</tt><tt class="descname">is_builtin</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#imp.is_builtin" title="Permalink to this definition">¶</a></dt>
<dd>Return <tt class="docutils literal"><span class="pre">1</span></tt> if there is a built-in module called <em>name</em> which can be
initialized again. Return <tt class="docutils literal"><span class="pre">-1</span></tt> if there is a built-in module called <em>name</em>
which cannot be initialized again (see <a title="imp.init_builtin" class="reference internal" href="#imp.init_builtin"><tt class="xref docutils literal"><span class="pre">init_builtin()</span></tt></a>). Return <tt class="docutils literal"><span class="pre">0</span></tt> if
there is no built-in module called <em>name</em>.</dd></dl>
<dl class="function">
<dt id="imp.is_frozen">
<tt class="descclassname">imp.</tt><tt class="descname">is_frozen</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#imp.is_frozen" title="Permalink to this definition">¶</a></dt>
<dd>Return <tt class="xref docutils literal"><span class="pre">True</span></tt> if there is a frozen module (see <a title="imp.init_frozen" class="reference internal" href="#imp.init_frozen"><tt class="xref docutils literal"><span class="pre">init_frozen()</span></tt></a>) called
<em>name</em>, or <tt class="xref docutils literal"><span class="pre">False</span></tt> if there is no such module.</dd></dl>
<dl class="function">
<dt id="imp.load_compiled">
<tt class="descclassname">imp.</tt><tt class="descname">load_compiled</tt><big>(</big><em>name</em>, <em>pathname</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#imp.load_compiled" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-351">Load and initialize a module implemented as a byte-compiled code file and return
its module object. If the module was already initialized, it will be
initialized <em>again</em>. The <em>name</em> argument is used to create or access a module
object. The <em>pathname</em> argument points to the byte-compiled code file. The
<em>file</em> argument is the byte-compiled code file, open for reading in binary mode,
from the beginning. It must currently be a real file object, not a user-defined
class emulating a file.</p>
</dd></dl>
<dl class="function">
<dt id="imp.load_dynamic">
<tt class="descclassname">imp.</tt><tt class="descname">load_dynamic</tt><big>(</big><em>name</em>, <em>pathname</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#imp.load_dynamic" title="Permalink to this definition">¶</a></dt>
<dd>Load and initialize a module implemented as a dynamically loadable shared
library and return its module object. If the module was already initialized, it
will be initialized <em>again</em>. Re-initialization involves copying the <tt class="docutils literal"><span class="pre">__dict__</span></tt>
attribute of the cached instance of the module over the value used in the module
cached in <tt class="docutils literal"><span class="pre">sys.modules</span></tt>. The <em>pathname</em> argument must point to the shared
library. The <em>name</em> argument is used to construct the name of the
initialization function: an external C function called <tt class="docutils literal"><span class="pre">initname()</span></tt> in the
shared library is called. The optional <em>file</em> argument is ignored. (Note:
using shared libraries is highly system dependent, and not all systems support
it.)</dd></dl>
<dl class="function">
<dt id="imp.load_source">
<tt class="descclassname">imp.</tt><tt class="descname">load_source</tt><big>(</big><em>name</em>, <em>pathname</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#imp.load_source" title="Permalink to this definition">¶</a></dt>
<dd>Load and initialize a module implemented as a Python source file and return its
module object. If the module was already initialized, it will be initialized
<em>again</em>. The <em>name</em> argument is used to create or access a module object. The
<em>pathname</em> argument points to the source file. The <em>file</em> argument is the
source file, open for reading as text, from the beginning. It must currently be
a real file object, not a user-defined class emulating a file. Note that if a
properly matching byte-compiled file (with suffix <tt class="docutils literal"><span class="pre">.pyc</span></tt> or <tt class="docutils literal"><span class="pre">.pyo</span></tt>)
exists, it will be used instead of parsing the given source file.</dd></dl>
<dl class="class">
<dt id="imp.NullImporter">
<em class="property">
class </em><tt class="descclassname">imp.</tt><tt class="descname">NullImporter</tt><big>(</big><em>path_string</em><big>)</big><a class="headerlink" href="#imp.NullImporter" title="Permalink to this definition">¶</a></dt>
<dd><p>The <a title="imp.NullImporter" class="reference internal" href="#imp.NullImporter"><tt class="xref docutils literal"><span class="pre">NullImporter</span></tt></a> type is a <span class="target" id="index-352"></span><a class="reference external" href="http://www.python.org/dev/peps/pep-0302"><strong>PEP 302</strong></a> import hook that handles
non-directory path strings by failing to find any modules. Calling this type
with an existing directory or empty string raises <a title="exceptions.ImportError" class="reference external" href="exceptions.html#exceptions.ImportError"><tt class="xref docutils literal"><span class="pre">ImportError</span></tt></a>.
Otherwise, a <a title="imp.NullImporter" class="reference internal" href="#imp.NullImporter"><tt class="xref docutils literal"><span class="pre">NullImporter</span></tt></a> instance is returned.</p>
<p>Python adds instances of this type to <tt class="docutils literal"><span class="pre">sys.path_importer_cache</span></tt> for any path
entries that are not directories and are not handled by any other path hooks on
<tt class="docutils literal"><span class="pre">sys.path_hooks</span></tt>. Instances have only one method:</p>
<dl class="method">
<dt id="imp.NullImporter.find_module">
<tt class="descname">find_module</tt><big>(</big><em>fullname</em><span class="optional">[</span>, <em>path</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#imp.NullImporter.find_module" title="Permalink to this definition">¶</a></dt>
<dd>This method always returns <tt class="xref docutils literal"><span class="pre">None</span></tt>, indicating that the requested module could
not be found.</dd></dl>
</dd></dl>
<div class="section" id="examples">
<span id="examples-imp"></span><h2>29.1.1. Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
<p>The following function emulates what was the standard import statement up to
Python 1.4 (no hierarchical module names). (This <em>implementation</em> wouldn’t work
in that version, since <a title="imp.find_module" class="reference internal" href="#imp.find_module"><tt class="xref docutils literal"><span class="pre">find_module()</span></tt></a> has been extended and
<a title="imp.load_module" class="reference internal" href="#imp.load_module"><tt class="xref docutils literal"><span class="pre">load_module()</span></tt></a> has been added in 1.4.)</p>
<div class="highlight-python3"><pre>import imp
import sys
def __import__(name, globals=None, locals=None, fromlist=None):
# Fast path: see if the module has already been imported.
try:
return sys.modules[name]
except KeyError:
pass
# If any of the following calls raises an exception,
# there's a problem we can't handle -- let the caller handle it.
fp, pathname, description = imp.find_module(name)
try:
return imp.load_module(name, fp, pathname, description)
finally:
# Since we may exit via an exception, close fp explicitly.
if fp:
fp.close()</pre>
</div>
<p id="index-353">A more complete example that implements hierarchical module names and includes a
<a title="imp.reload" class="reference internal" href="#imp.reload"><tt class="xref docutils literal"><span class="pre">reload()</span></tt></a> function can be found in the module <tt class="xref docutils literal"><span class="pre">knee</span></tt>. The <tt class="xref docutils literal"><span class="pre">knee</span></tt>
module can be found in <tt class="docutils literal"><span class="pre">Demo/imputil/</span></tt> in the Python source distribution.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper">
<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference external" href="">29.1. <tt class="docutils literal"><span class="pre">imp</span></tt> — Access the <tt class="docutils literal"><span class="pre">import</span></tt> internals</a><ul>
<li><a class="reference external" href="#examples">29.1.1. Examples</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="modules.html"
title="previous chapter">29. Importing Modules</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="zipimport.html"
title="next chapter">29.2. <tt class="docutils literal"><span class="pre">zipimport</span></tt> — Import modules from Zip archives</a></p>
<h3>This Page</h3>
<ul class="this-page-menu">
<li><a href="../_sources/library/imp.txt"
rel="nofollow">Show Source</a></li>
</ul>
<div id="searchbox" style="display: none">
<h3>Quick search</h3>
<form class="search" action="../search.html" method="get">
<input type="text" name="q" size="18" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
<p class="searchtip" style="font-size: 90%">
Enter search terms or a module, class or function name.
</p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../genindex.html" title="General Index"
>index</a></li>
<li class="right" >
<a href="../modindex.html" title="Global Module Index"
>modules</a> |</li>
<li class="right" >
<a href="zipimport.html" title="29.2. zipimport — Import modules from Zip archives"
>next</a> |</li>
<li class="right" >
<a href="modules.html" title="29. Importing Modules"
>previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="../index.html">Python v3.1.1 documentation</a> »</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="modules.html" >29. Importing Modules</a> »</li>
</ul>
</div>
<div class="footer">
© <a href="../copyright.html">Copyright</a> 1990-2009, Python Software Foundation.
<br />
The Python Software Foundation is a non-profit corporation.
<a href="http://www.python.org/psf/donations/">Please donate.</a>
<br />
Last updated on Aug 16, 2009.
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 0.6.2.
</div>
</body>
</html>
distrib
>
Mandriva
>
2010.0
>
i586
>
media
>
contrib-release
>
by-pkgid
>
e870e6598e1c7e3918555a3d0ba5f3d4
>
files
>
662
