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<div class="section" id="module-Bastion">
<h1>30.2. <tt class="xref docutils literal"><span class="pre">Bastion</span></tt> — Restricting access to objects<a class="headerlink" href="#module-Bastion" title="Permalink to this headline">¶</a></h1>
<p class="deprecated">
<span class="versionmodified">Deprecated since version 2.6: </span>The <tt class="xref docutils literal"><span class="pre">Bastion</span></tt> module has been removed in Python 3.0.</p>
<p class="versionchanged">
<span class="versionmodified">Changed in version 2.3: </span>Disabled module.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The documentation has been left in place to help in reading old code that uses
the module.</p>
</div>
<p>According to the dictionary, a bastion is “a fortified area or position”, or
“something that is considered a stronghold.” It’s a suitable name for this
module, which provides a way to forbid access to certain attributes of an
object. It must always be used with the <a title="Basic restricted execution framework. (deprecated)" class="reference external" href="rexec.html#module-rexec"><tt class="xref docutils literal"><span class="pre">rexec</span></tt></a> module, in order to allow
restricted-mode programs access to certain safe attributes of an object, while
denying access to other, unsafe attributes.</p>
<dl class="function">
<dt id="Bastion.Bastion">
<tt class="descclassname">Bastion.</tt><tt class="descname">Bastion</tt><big>(</big><em>object</em><span class="optional">[</span>, <em>filter</em><span class="optional">[</span>, <em>name</em><span class="optional">[</span>, <em>class</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#Bastion.Bastion" title="Permalink to this definition">¶</a></dt>
<dd><p>Protect the object <em>object</em>, returning a bastion for the object. Any attempt to
access one of the object’s attributes will have to be approved by the <em>filter</em>
function; if the access is denied an <a title="exceptions.AttributeError" class="reference external" href="exceptions.html#exceptions.AttributeError"><tt class="xref docutils literal"><span class="pre">AttributeError</span></tt></a> exception will be
raised.</p>
<p>If present, <em>filter</em> must be a function that accepts a string containing an
attribute name, and returns true if access to that attribute will be permitted;
if <em>filter</em> returns false, the access is denied. The default filter denies
access to any function beginning with an underscore (<tt class="docutils literal"><span class="pre">'_'</span></tt>). The bastion’s
string representation will be <tt class="docutils literal"><span class="pre"><Bastion</span> <span class="pre">for</span> <span class="pre">name></span></tt> if a value for <em>name</em> is
provided; otherwise, <tt class="docutils literal"><span class="pre">repr(object)</span></tt> will be used.</p>
<p><em>class</em>, if present, should be a subclass of <a title="Bastion.BastionClass" class="reference internal" href="#Bastion.BastionClass"><tt class="xref docutils literal"><span class="pre">BastionClass</span></tt></a>; see the
code in <tt class="docutils literal"><span class="pre">bastion.py</span></tt> for the details. Overriding the default
<a title="Bastion.BastionClass" class="reference internal" href="#Bastion.BastionClass"><tt class="xref docutils literal"><span class="pre">BastionClass</span></tt></a> will rarely be required.</p>
</dd></dl>
<dl class="class">
<dt id="Bastion.BastionClass">
<em class="property">class </em><tt class="descclassname">Bastion.</tt><tt class="descname">BastionClass</tt><big>(</big><em>getfunc</em>, <em>name</em><big>)</big><a class="headerlink" href="#Bastion.BastionClass" title="Permalink to this definition">¶</a></dt>
<dd>Class which actually implements bastion objects. This is the default class used
by <a title="Bastion.Bastion" class="reference internal" href="#Bastion.Bastion"><tt class="xref docutils literal"><span class="pre">Bastion()</span></tt></a>. The <em>getfunc</em> parameter is a function which returns the
value of an attribute which should be exposed to the restricted execution
environment when called with the name of the attribute as the only parameter.
<em>name</em> is used to construct the <a title="repr" class="reference external" href="functions.html#repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a> of the <a title="Bastion.BastionClass" class="reference internal" href="#Bastion.BastionClass"><tt class="xref docutils literal"><span class="pre">BastionClass</span></tt></a>
instance.</dd></dl>
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