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<title>19.3 Python Abstract Syntax
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<H1><A NAME=
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19.3 Python Abstract Syntax
</A>
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.
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.
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.
The
<tt class=
"module">transformer
</tt> module was created by Greg
Stein
<a id='l2h-
5025' xml:id='l2h-
5025'
></a> and Bill Tutt
<a id='l2h-
5026' xml:id='l2h-
5026'
></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.
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<A NAME=
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<LI><A href=
"module-compiler.ast.html">19.3.1 AST Nodes
</a>
<LI><A href=
"node794.html">19.3.2 Assignment nodes
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<LI><A href=
"node795.html">19.3.3 Examples
</a>
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<span class=
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