<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>19.3 Python Abstract Syntax</title> <META NAME="description" CONTENT="19.3 Python Abstract Syntax"> <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="module-compiler.visitor.html"> <LINK REL="previous" HREF="node573.html"> <LINK REL="up" href="compiler.html"> <LINK REL="next" href="module-compiler.ast.html"> </head> <body> <DIV CLASS="navigation"> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td><A HREF="node573.html"><img src="../icons/previous.gif" border="0" height="32" alt="Previous Page" width="32"></A></td> <td><A href="compiler.html"><img src="../icons/up.gif" border="0" height="32" alt="Up One Level" width="32"></A></td> <td><A href="module-compiler.ast.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="node573.html">19.2 Limitations</A> <b class="navlabel">Up:</b> <a class="sectref" href="compiler.html">19. Python compiler package</A> <b class="navlabel">Next:</b> <a class="sectref" href="module-compiler.ast.html">19.3.1 AST Nodes</A> <br><hr> </DIV> <!--End of Navigation Panel--> <H1><A NAME="SECTION0021300000000000000000"> 19.3 Python Abstract Syntax</A> </H1> <P> The <tt class="module">compiler.ast</tt> module defines an abstract syntax for Python. In the abstract syntax tree, each node represents a syntactic construct. The root of the tree is <tt class="class">Module</tt> object. <P> The abstract syntax offers a higher level interface to parsed Python source code. The <a class="ulink" href="http://www.python.org/doc/current/lib/module-parser.html" ><tt class="module">parser</tt></a> module and the compiler written in C for the Python interpreter use a concrete syntax tree. The concrete syntax is tied closely to the grammar description used for the Python parser. Instead of a single node for a construct, there are often several levels of nested nodes that are introduced by Python's precedence rules. <P> The abstract syntax tree is created by the <tt class="module">compiler.transformer</tt> module. The transformer relies on the builtin Python parser to generate a concrete syntax tree. It generates an abstract syntax tree from the concrete tree. <P> The <tt class="module">transformer</tt> module was created by Greg Stein<a name="l2h-3842"> </a>and Bill Tutt<a name="l2h-3843"> </a>for an experimental Python-to-C compiler. The current version contains a number of modifications and improvements, but the basic form of the abstract syntax and of the transformer are due to Stein and Tutt. <P> <p><hr> <!--Table of Child-Links--> <A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a> <UL CLASS="ChildLinks"> <LI><A href="module-compiler.ast.html">19.3.1 AST Nodes</a> <LI><A href="node576.html">19.3.2 Assignment nodes</a> <LI><A href="node577.html">19.3.3 Examples</a> </ul> <!--End of Table of Child-Links--> <DIV CLASS="navigation"> <p><hr> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td><A HREF="node573.html"><img src="../icons/previous.gif" border="0" height="32" alt="Previous Page" width="32"></A></td> <td><A href="compiler.html"><img src="../icons/up.gif" border="0" height="32" alt="Up One Level" width="32"></A></td> <td><A href="module-compiler.ast.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="node573.html">19.2 Limitations</A> <b class="navlabel">Up:</b> <a class="sectref" href="compiler.html">19. Python compiler package</A> <b class="navlabel">Next:</b> <a class="sectref" href="module-compiler.ast.html">19.3.1 AST Nodes</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>
