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56 | 19.3 Python Abstract Syntax</A> | |
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58 | ||
59 | <P> | |
60 | The <tt class="module">compiler.ast</tt> module defines an abstract syntax for | |
61 | Python. In the abstract syntax tree, each node represents a syntactic | |
62 | construct. The root of the tree is <tt class="class">Module</tt> object. | |
63 | ||
64 | <P> | |
65 | The abstract syntax offers a higher level interface to parsed Python | |
66 | source code. The <a class="ulink" href="http://www.python.org/doc/current/lib/module-parser.html" | |
67 | ><tt class="module">parser</tt></a> | |
68 | module and the compiler written in C for the Python interpreter use a | |
69 | concrete syntax tree. The concrete syntax is tied closely to the | |
70 | grammar description used for the Python parser. Instead of a single | |
71 | node for a construct, there are often several levels of nested nodes | |
72 | that are introduced by Python's precedence rules. | |
73 | ||
74 | <P> | |
75 | The abstract syntax tree is created by the | |
76 | <tt class="module">compiler.transformer</tt> module. The transformer relies on the | |
77 | builtin Python parser to generate a concrete syntax tree. It | |
78 | generates an abstract syntax tree from the concrete tree. | |
79 | ||
80 | <P> | |
81 | The <tt class="module">transformer</tt> module was created by Greg | |
82 | Stein<a id='l2h-5025' xml:id='l2h-5025'></a> and Bill Tutt<a id='l2h-5026' xml:id='l2h-5026'></a> for an | |
83 | experimental Python-to-C compiler. The current version contains a | |
84 | number of modifications and improvements, but the basic form of the | |
85 | abstract syntax and of the transformer are due to Stein and Tutt. | |
86 | ||
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