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<!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>30.1. imp — Access the import internals — Python 2.7.5 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: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.5 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 2.7.5 documentation" href="../index.html" /> <link rel="up" title="30. Importing Modules" href="modules.html" /> <link rel="next" title="30.2. importlib – Convenience wrappers for __import__()" href="importlib.html" /> <link rel="prev" title="30. Importing Modules" href="modules.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </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="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="importlib.html" title="30.2. importlib – Convenience wrappers for __import__()" accesskey="N">next</a> |</li> <li class="right" > <a href="modules.html" title="30. 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="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="modules.html" accesskey="U">30. Importing Modules</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-imp"> <span id="imp-access-the-import-internals"></span><h1>30.1. <a class="reference internal" href="#module-imp" title="imp: Access the implementation of the import statement."><tt class="xref py py-mod docutils literal"><span class="pre">imp</span></tt></a> — Access the <a class="reference internal" href="../reference/simple_stmts.html#import"><tt class="xref std std-keyword 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-0">This module provides an interface to the mechanisms used to implement the <a class="reference internal" href="../reference/simple_stmts.html#import"><tt class="xref std std-keyword 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-1">Return the magic string value used to recognize byte-compiled code files (<tt class="file 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><p>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 class="reference internal" href="functions.html#open" title="open"><tt class="xref py py-func 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 class="reference internal" href="#imp.PY_SOURCE" title="imp.PY_SOURCE"><tt class="xref py py-const docutils literal"><span class="pre">PY_SOURCE</span></tt></a>, <a class="reference internal" href="#imp.PY_COMPILED" title="imp.PY_COMPILED"><tt class="xref py py-const docutils literal"><span class="pre">PY_COMPILED</span></tt></a>, or <a class="reference internal" href="#imp.C_EXTENSION" title="imp.C_EXTENSION"><tt class="xref py py-const docutils literal"><span class="pre">C_EXTENSION</span></tt></a>, described below.</p> </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="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 class="reference internal" href="#imp.C_BUILTIN" title="imp.C_BUILTIN"><tt class="xref py py-const docutils literal"><span class="pre">C_BUILTIN</span></tt></a>), then a frozen module (<a class="reference internal" href="#imp.PY_FROZEN" title="imp.PY_FROZEN"><tt class="xref py py-const 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 class="reference internal" href="#imp.get_suffixes" title="imp.get_suffixes"><tt class="xref py py-func 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 class="reference internal" href="#imp.get_suffixes" title="imp.get_suffixes"><tt class="xref py py-func 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="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 class="reference internal" href="exceptions.html#exceptions.ImportError" title="exceptions.ImportError"><tt class="xref py py-exc 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="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 class="reference internal" href="#imp.PKG_DIRECTORY" title="imp.PKG_DIRECTORY"><tt class="xref py py-const 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.M</em>, that is, submodule <em>M</em> of package <em>P</em>, use <a class="reference internal" href="#imp.find_module" title="imp.find_module"><tt class="xref py py-func docutils literal"><span class="pre">find_module()</span></tt></a> and <a class="reference internal" href="#imp.load_module" title="imp.load_module"><tt class="xref py py-func docutils literal"><span class="pre">load_module()</span></tt></a> to find and load package <em>P</em>, and then use <a class="reference internal" href="#imp.find_module" title="imp.find_module"><tt class="xref py py-func 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 id="index-2">Load a module that was previously found by <a class="reference internal" href="#imp.find_module" title="imp.find_module"><tt class="xref py py-func 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 is equivalent to a <a class="reference internal" href="functions.html#reload" title="reload"><tt class="xref py py-func docutils literal"><span class="pre">reload()</span></tt></a>! 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="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 class="reference internal" href="#imp.get_suffixes" title="imp.get_suffixes"><tt class="xref py py-func 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 class="reference internal" href="exceptions.html#exceptions.ImportError" title="exceptions.ImportError"><tt class="xref py py-exc 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="docutils literal"><span class="pre">None</span></tt>, even when an exception is raised. This is best done using a <a class="reference internal" href="../reference/compound_stmts.html#try"><tt class="xref std std-keyword docutils literal"><span class="pre">try</span></tt></a> ... <a class="reference internal" href="../reference/compound_stmts.html#finally"><tt class="xref std std-keyword 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><p>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>.</p> </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="docutils literal"><span class="pre">True</span></tt> if the import lock is currently held, else <tt class="docutils literal"><span class="pre">False</span></tt>. On platforms without threads, always return <tt class="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.</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> <p class="versionadded"> <span class="versionmodified">New in version 2.3.</span></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><p>Release the interpreter’s import lock. On platforms without threads, this function does nothing.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.3.</span></p> </dd></dl> <p>The following constants with integer values, defined in this module, are used to indicate the search result of <a class="reference internal" href="#imp.find_module" title="imp.find_module"><tt class="xref py py-func 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><p>The module was found as a source file.</p> </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><p>The module was found as a compiled code object file.</p> </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><p>The module was found as dynamically loadable shared library.</p> </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><p>The module was found as a package directory.</p> </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><p>The module was found as a built-in module.</p> </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><p>The module was found as a frozen module (see <a class="reference internal" href="#imp.init_frozen" title="imp.init_frozen"><tt class="xref py py-func docutils literal"><span class="pre">init_frozen()</span></tt></a>).</p> </dd></dl> <p>The following constant and functions are obsolete; their functionality is available through <a class="reference internal" href="#imp.find_module" title="imp.find_module"><tt class="xref py py-func docutils literal"><span class="pre">find_module()</span></tt></a> or <a class="reference internal" href="#imp.load_module" title="imp.load_module"><tt class="xref py py-func 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><p>Unused.</p> </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><p>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="docutils literal"><span class="pre">None</span></tt> is returned.</p> </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><p>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="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 class="program">freeze</strong> utility. See <tt class="file docutils literal"><span class="pre">Tools/freeze/</span></tt> for now.)</p> </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><p>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 class="reference internal" href="#imp.init_builtin" title="imp.init_builtin"><tt class="xref py py-func 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>.</p> </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><p>Return <tt class="docutils literal"><span class="pre">True</span></tt> if there is a frozen module (see <a class="reference internal" href="#imp.init_frozen" title="imp.init_frozen"><tt class="xref py py-func docutils literal"><span class="pre">init_frozen()</span></tt></a>) called <em>name</em>, or <tt class="docutils literal"><span class="pre">False</span></tt> if there is no such module.</p> </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-3">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><p>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.)</p> <div class="impl-detail compound"> <p><strong>CPython implementation detail:</strong> The import internals identify extension modules by filename, so doing <tt class="docutils literal"><span class="pre">foo</span> <span class="pre">=</span> <span class="pre">load_dynamic("foo",</span> <span class="pre">"mod.so")</span></tt> and <tt class="docutils literal"><span class="pre">bar</span> <span class="pre">=</span> <span class="pre">load_dynamic("bar",</span> <span class="pre">"mod.so")</span></tt> will result in both foo and bar referring to the same module, regardless of whether or not <tt class="docutils literal"><span class="pre">mod.so</span></tt> exports an <tt class="docutils literal"><span class="pre">initbar</span></tt> function. On systems which support them, symlinks can be used to import multiple modules from the same shared library, as each reference to the module will use a different file name.</p> </div> </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><p>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="file docutils literal"><span class="pre">.pyc</span></tt> or <tt class="file docutils literal"><span class="pre">.pyo</span></tt>) exists, it will be used instead of parsing the given source file.</p> </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 class="reference internal" href="#imp.NullImporter" title="imp.NullImporter"><tt class="xref py py-class docutils literal"><span class="pre">NullImporter</span></tt></a> type is a <span class="target" id="index-4"></span><a class="pep 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 class="reference internal" href="exceptions.html#exceptions.ImportError" title="exceptions.ImportError"><tt class="xref py py-exc docutils literal"><span class="pre">ImportError</span></tt></a>. Otherwise, a <a class="reference internal" href="#imp.NullImporter" title="imp.NullImporter"><tt class="xref py py-class 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><p>This method always returns <tt class="docutils literal"><span class="pre">None</span></tt>, indicating that the requested module could not be found.</p> </dd></dl> <p class="versionadded"> <span class="versionmodified">New in version 2.5.</span></p> </dd></dl> <div class="section" id="examples"> <span id="examples-imp"></span><h2>30.1.1. 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 class="reference internal" href="#imp.find_module" title="imp.find_module"><tt class="xref py py-func docutils literal"><span class="pre">find_module()</span></tt></a> has been extended and <a class="reference internal" href="#imp.load_module" title="imp.load_module"><tt class="xref py py-func docutils literal"><span class="pre">load_module()</span></tt></a> has been added in 1.4.)</p> <div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">imp</span> <span class="kn">import</span> <span class="nn">sys</span> <span class="k">def</span> <span class="nf">__import__</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="nb">globals</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="nb">locals</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">fromlist</span><span class="o">=</span><span class="bp">None</span><span class="p">):</span> <span class="c"># Fast path: see if the module has already been imported.</span> <span class="k">try</span><span class="p">:</span> <span class="k">return</span> <span class="n">sys</span><span class="o">.</span><span class="n">modules</span><span class="p">[</span><span class="n">name</span><span class="p">]</span> <span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span> <span class="k">pass</span> <span class="c"># If any of the following calls raises an exception,</span> <span class="c"># there's a problem we can't handle -- let the caller handle it.</span> <span class="n">fp</span><span class="p">,</span> <span class="n">pathname</span><span class="p">,</span> <span class="n">description</span> <span class="o">=</span> <span class="n">imp</span><span class="o">.</span><span class="n">find_module</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="k">try</span><span class="p">:</span> <span class="k">return</span> <span class="n">imp</span><span class="o">.</span><span class="n">load_module</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">fp</span><span class="p">,</span> <span class="n">pathname</span><span class="p">,</span> <span class="n">description</span><span class="p">)</span> <span class="k">finally</span><span class="p">:</span> <span class="c"># Since we may exit via an exception, close fp explicitly.</span> <span class="k">if</span> <span class="n">fp</span><span class="p">:</span> <span class="n">fp</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></div> </div> <p id="index-5">A more complete example that implements hierarchical module names and includes a <a class="reference internal" href="functions.html#reload" title="reload"><tt class="xref py py-func docutils literal"><span class="pre">reload()</span></tt></a> function can be found in the module <tt class="xref py py-mod docutils literal"><span class="pre">knee</span></tt>. The <tt class="xref py py-mod docutils literal"><span class="pre">knee</span></tt> module can be found in <tt class="file 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 internal" href="#">30.1. <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 internal" href="#examples">30.1.1. Examples</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="modules.html" title="previous chapter">30. Importing Modules</a></p> <h4>Next topic</h4> <p class="topless"><a href="importlib.html" title="next chapter">30.2. <tt class="docutils literal"><span class="pre">importlib</span></tt> – Convenience wrappers for <tt class="docutils literal"><span class="pre">__import__()</span></tt></a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <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" /> <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="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="importlib.html" title="30.2. importlib – Convenience wrappers for __import__()" >next</a> |</li> <li class="right" > <a href="modules.html" title="30. Importing Modules" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="modules.html" >30. Importing Modules</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2019, 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 Jul 03, 2019. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>
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