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<H1><A NAME="SECTION0052200000000000000000">
3.22 <tt class="module">code</tt> --
Interpreter base classes</A>
</H1>
<P>
<P>
The <code>code</code> module provides facilities to implement
read-eval-print loops in Python. Two classes and convenience
functions are included which can be used to build applications which
provide an interactive interpreter prompt.
<P>
<dl><dt><b><span class="typelabel">class</span> <a name="l2h-597"><tt class="class">InteractiveInterpreter</tt></a></b>(<big>[</big><var>locals</var><big>]</big>)
<dd>
This class deals with parsing and interpreter state (the user's
namespace); it does not deal with input buffering or prompting or
input file naming (the filename is always passed in explicitly).
The optional <var>locals</var> argument specifies the dictionary in
which code will be executed; it defaults to a newly created
dictionary with key <code>'__name__'</code> set to <code>'__console__'</code>
and key <code>'__doc__'</code> set to <code>None</code>.
</dl>
<P>
<dl><dt><b><span class="typelabel">class</span> <a name="l2h-598"><tt class="class">InteractiveConsole</tt></a></b>(<big>[</big><var>locals</var><big>[</big><var>, filename</var><big>]</big><big>]</big>)
<dd>
Closely emulate the behavior of the interactive Python interpreter.
This class builds on <tt class="class">InteractiveInterpreter</tt> and adds
prompting using the familiar <code>sys.ps1</code> and <code>sys.ps2</code>, and
input buffering.
</dl>
<P>
<dl><dt><b><a name="l2h-599"><tt class="function">interact</tt></a></b>(<big>[</big><var>banner</var><big>[</big><var>,
readfunc</var><big>[</big><var>, local</var><big>]</big><big>]</big><big>]</big>)
<dd>
Convenience function to run a read-eval-print loop. This creates a
new instance of <tt class="class">InteractiveConsole</tt> and sets <var>readfunc</var>
to be used as the <tt class="method">raw_input()</tt> method, if provided. If
<var>local</var> is provided, it is passed to the
<tt class="class">InteractiveConsole</tt> constructor for use as the default
namespace for the interpreter loop. The <tt class="method">interact()</tt> method
of the instance is then run with <var>banner</var> passed as the banner
to use, if provided. The console object is discarded after use.
</dl>
<P>
<dl><dt><b><a name="l2h-600"><tt class="function">compile_command</tt></a></b>(<var>source</var><big>[</big><var>,
filename</var><big>[</big><var>, symbol</var><big>]</big><big>]</big>)
<dd>
This function is useful for programs that want to emulate Python's
interpreter main loop (a.k.a. the read-eval-print loop). The tricky
part is to determine when the user has entered an incomplete command
that can be completed by entering more text (as opposed to a
complete command or a syntax error). This function
<i>almost</i> always makes the same decision as the real interpreter
main loop.
<P>
<var>source</var> is the source string; <var>filename</var> is the optional
filename from which source was read, defaulting to <code>'<input>'</code>;
and <var>symbol</var> is the optional grammar start symbol, which should
be either <code>'single'</code> (the default) or <code>'eval'</code>.
<P>
Returns a code object (the same as <code>compile(<var>source</var>,
<var>filename</var>, <var>symbol</var>)</code>) if the command is complete and
valid; <code>None</code> if the command is incomplete; raises
<tt class="exception">SyntaxError</tt> if the command is complete and contains a
syntax error, or raises <tt class="exception">OverflowError</tt> or
<tt class="exception">ValueError</tt> if the command cotains an invalid literal.
</dl>
<P>
<p><hr>
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<LI><A href="interpreter-objects.html">3.22.1 Interactive Interpreter Objects</a>
<LI><A href="console-objects.html">3.22.2 Interactive Console Objects</a>
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<span class="release-info">Release 2.2, documentation updated on December 21, 2001.</span>
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