<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>17.1.1 RExec Objects </title>
<META NAME="description" CONTENT="17.1.1 RExec Objects ">
<META NAME="keywords" CONTENT="lib">
<META NAME="resource-type" CONTENT="document">
<META NAME="distribution" CONTENT="global">
<meta http-equiv="Content-Type" content="text/html; charset=">
<link rel="STYLESHEET" href="lib.css">
<link rel="first" href="lib.html">
<link rel="contents" href="contents.html" title="Contents">
<link rel="index" href="genindex.html" title="Index">
<LINK REL="next" href="rexec-extension.html">
<LINK REL="previous" href="module-rexec.html">
<LINK REL="up" href="module-rexec.html">
<LINK REL="next" href="rexec-extension.html">
</head>
<body>
<DIV CLASS="navigation">
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td><A href="module-rexec.html"><img src="../icons/previous.gif"
border="0" height="32"
alt="Previous Page" width="32"></A></td>
<td><A href="module-rexec.html"><img src="../icons/up.gif"
border="0" height="32"
alt="Up One Level" width="32"></A></td>
<td><A href="rexec-extension.html"><img src="../icons/next.gif"
border="0" height="32"
alt="Next Page" width="32"></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td><A href="contents.html"><img src="../icons/contents.gif"
border="0" height="32"
alt="Contents" width="32"></A></td>
<td><a href="modindex.html" title="Module Index"><img src="../icons/modules.gif"
border="0" height="32"
alt="Module Index" width="32"></a></td>
<td><A href="genindex.html"><img src="../icons/index.gif"
border="0" height="32"
alt="Index" width="32"></A></td>
</tr></table>
<b class="navlabel">Previous:</b> <a class="sectref" href="module-rexec.html">17.1 rexec </A>
<b class="navlabel">Up:</b> <a class="sectref" href="module-rexec.html">17.1 rexec </A>
<b class="navlabel">Next:</b> <a class="sectref" href="rexec-extension.html">17.1.2 Defining restricted environments</A>
<br><hr>
</DIV>
<!--End of Navigation Panel-->
<H2><A NAME="SECTION0019110000000000000000"> </A>
<BR>
17.1.1 RExec Objects
</H2>
<P>
<tt class="class">RExec</tt> instances support the following methods:
<P>
<dl><dt><b><a name="l2h-3744"><tt class="method">r_eval</tt></a></b>(<var>code</var>)
<dd>
<var>code</var> must either be a string containing a Python expression, or
a compiled code object, which will be evaluated in the restricted
environment's <tt class="module">__main__</tt> module. The value of the expression or
code object will be returned.
</dl>
<P>
<dl><dt><b><a name="l2h-3745"><tt class="method">r_exec</tt></a></b>(<var>code</var>)
<dd>
<var>code</var> must either be a string containing one or more lines of
Python code, or a compiled code object, which will be executed in the
restricted environment's <tt class="module">__main__</tt> module.
</dl>
<P>
<dl><dt><b><a name="l2h-3746"><tt class="method">r_execfile</tt></a></b>(<var>filename</var>)
<dd>
Execute the Python code contained in the file <var>filename</var> in the
restricted environment's <tt class="module">__main__</tt> module.
</dl>
<P>
Methods whose names begin with "<tt class="samp">s_</tt>" are similar to the functions
beginning with "<tt class="samp">r_</tt>", but the code will be granted access to
restricted versions of the standard I/O streams <code>sys.stdin</code>,
<code>sys.stderr</code>, and <code>sys.stdout</code>.
<P>
<dl><dt><b><a name="l2h-3747"><tt class="method">s_eval</tt></a></b>(<var>code</var>)
<dd>
<var>code</var> must be a string containing a Python expression, which will
be evaluated in the restricted environment.
</dl>
<P>
<dl><dt><b><a name="l2h-3748"><tt class="method">s_exec</tt></a></b>(<var>code</var>)
<dd>
<var>code</var> must be a string containing one or more lines of Python code,
which will be executed in the restricted environment.
</dl>
<P>
<dl><dt><b><a name="l2h-3749"><tt class="method">s_execfile</tt></a></b>(<var>code</var>)
<dd>
Execute the Python code contained in the file <var>filename</var> in the
restricted environment.
</dl>
<P>
<tt class="class">RExec</tt> objects must also support various methods which will be
implicitly called by code executing in the restricted environment.
Overriding these methods in a subclass is used to change the policies
enforced by a restricted environment.
<P>
<dl><dt><b><a name="l2h-3750"><tt class="method">r_import</tt></a></b>(<var>modulename</var><big>[</big><var>, globals</var><big>[</big><var>,
locals</var><big>[</big><var>, fromlist</var><big>]</big><big>]</big><big>]</big>)
<dd>
Import the module <var>modulename</var>, raising an <tt class="exception">ImportError</tt>
exception if the module is considered unsafe.
</dl>
<P>
<dl><dt><b><a name="l2h-3751"><tt class="method">r_open</tt></a></b>(<var>filename</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><big>]</big>)
<dd>
Method called when <tt class="function">open()</tt> is called in the restricted
environment. The arguments are identical to those of <tt class="function">open()</tt>,
and a file object (or a class instance compatible with file objects)
should be returned. <tt class="class">RExec</tt>'s default behaviour is allow opening
any file for reading, but forbidding any attempt to write a file. See
the example below for an implementation of a less restrictive
<tt class="method">r_open()</tt>.
</dl>
<P>
<dl><dt><b><a name="l2h-3752"><tt class="method">r_reload</tt></a></b>(<var>module</var>)
<dd>
Reload the module object <var>module</var>, re-parsing and re-initializing it.
</dl>
<P>
<dl><dt><b><a name="l2h-3753"><tt class="method">r_unload</tt></a></b>(<var>module</var>)
<dd>
Unload the module object <var>module</var> (remove it from the
restricted environment's <code>sys.modules</code> dictionary).
</dl>
<P>
And their equivalents with access to restricted standard I/O streams:
<P>
<dl><dt><b><a name="l2h-3754"><tt class="method">s_import</tt></a></b>(<var>modulename</var><big>[</big><var>, globals</var><big>[</big><var>,
locals</var><big>[</big><var>, fromlist</var><big>]</big><big>]</big><big>]</big>)
<dd>
Import the module <var>modulename</var>, raising an <tt class="exception">ImportError</tt>
exception if the module is considered unsafe.
</dl>
<P>
<dl><dt><b><a name="l2h-3755"><tt class="method">s_reload</tt></a></b>(<var>module</var>)
<dd>
Reload the module object <var>module</var>, re-parsing and re-initializing it.
</dl>
<P>
<dl><dt><b><a name="l2h-3756"><tt class="method">s_unload</tt></a></b>(<var>module</var>)
<dd>
Unload the module object <var>module</var>.
</dl>
<P>
<DIV CLASS="navigation">
<p><hr>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td><A href="module-rexec.html"><img src="../icons/previous.gif"
border="0" height="32"
alt="Previous Page" width="32"></A></td>
<td><A href="module-rexec.html"><img src="../icons/up.gif"
border="0" height="32"
alt="Up One Level" width="32"></A></td>
<td><A href="rexec-extension.html"><img src="../icons/next.gif"
border="0" height="32"
alt="Next Page" width="32"></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td><A href="contents.html"><img src="../icons/contents.gif"
border="0" height="32"
alt="Contents" width="32"></A></td>
<td><a href="modindex.html" title="Module Index"><img src="../icons/modules.gif"
border="0" height="32"
alt="Module Index" width="32"></a></td>
<td><A href="genindex.html"><img src="../icons/index.gif"
border="0" height="32"
alt="Index" width="32"></A></td>
</tr></table>
<b class="navlabel">Previous:</b> <a class="sectref" href="module-rexec.html">17.1 rexec </A>
<b class="navlabel">Up:</b> <a class="sectref" href="module-rexec.html">17.1 rexec </A>
<b class="navlabel">Next:</b> <a class="sectref" href="rexec-extension.html">17.1.2 Defining restricted environments</A>
<hr>
<span class="release-info">Release 2.2, documentation updated on December 21, 2001.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>
