[OpenSPARC-T2-SAM] / sam-t2 / devtools / v9 / html / python / lib / node795.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="prev" href="node794.html" />
<link rel="parent" href="node792.html" />
<link rel="next" href="module-compiler.visitor.html" />
<meta name='aesop' content='information' />
<title>19.3.3 Examples</title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="19.3.2 Assignment nodes"
  href="node794.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="19.3 Python Abstract Syntax"
  href="node792.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="19.4 Using Visitors to"
  href="module-compiler.visitor.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="node794.html">19.3.2 Assignment nodes</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="node792.html">19.3 Python Abstract Syntax</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="module-compiler.visitor.html">19.4 Using Visitors to</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H2><A NAME="SECTION0021330000000000000000">
19.3.3 Examples</A>
</H2>

<P>
This section shows several simple examples of ASTs for Python source
code.  The examples demonstrate how to use the <tt class="function">parse()</tt>
function, what the repr of an AST looks like, and how to access
attributes of an AST node.

<P>
The first module defines a single function.  Assume it is stored in
<span class="file">/tmp/doublelib.py</span>. 

<P>
<div class="verbatim"><pre>
"""This is an example module.

This is the docstring.
"""

def double(x):
    "Return twice the argument"
    return x * 2
</pre></div>

<P>
In the interactive interpreter session below, I have reformatted the
long AST reprs for readability.  The AST reprs use unqualified class
names.  If you want to create an instance from a repr, you must import
the class names from the <tt class="module">compiler.ast</tt> module.

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; import compiler
&gt;&gt;&gt; mod = compiler.parseFile("/tmp/doublelib.py")
&gt;&gt;&gt; mod
Module('This is an example module.\n\nThis is the docstring.\n', 
       Stmt([Function(None, 'double', ['x'], [], 0,
                      'Return twice the argument', 
                      Stmt([Return(Mul((Name('x'), Const(2))))]))]))
&gt;&gt;&gt; from compiler.ast import *
&gt;&gt;&gt; Module('This is an example module.\n\nThis is the docstring.\n', 
...    Stmt([Function(None, 'double', ['x'], [], 0,
...                   'Return twice the argument', 
...                   Stmt([Return(Mul((Name('x'), Const(2))))]))]))
Module('This is an example module.\n\nThis is the docstring.\n', 
       Stmt([Function(None, 'double', ['x'], [], 0,
                      'Return twice the argument', 
                      Stmt([Return(Mul((Name('x'), Const(2))))]))]))
&gt;&gt;&gt; mod.doc
'This is an example module.\n\nThis is the docstring.\n'
&gt;&gt;&gt; for node in mod.node.nodes:
...     print node
... 
Function(None, 'double', ['x'], [], 0, 'Return twice the argument',
         Stmt([Return(Mul((Name('x'), Const(2))))]))
&gt;&gt;&gt; func = mod.node.nodes[0]
&gt;&gt;&gt; func.code
Stmt([Return(Mul((Name('x'), Const(2))))])
</pre></div>

<P>

<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="19.3.2 Assignment nodes"
  href="node794.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="19.3 Python Abstract Syntax"
  href="node792.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="19.4 Using Visitors to"
  href="module-compiler.visitor.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="node794.html">19.3.2 Assignment nodes</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="node792.html">19.3 Python Abstract Syntax</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="module-compiler.visitor.html">19.4 Using Visitors to</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</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>
Commit	Line	Data
920dae64 AT	1	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
	2	<html>
	3	<head>
	4	<link rel="STYLESHEET" href="lib.css" type='text/css' />
	5	<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
	6	<link rel='start' href='../index.html' title='Python Documentation Index' />
	7	<link rel="first" href="lib.html" title='Python Library Reference' />
	8	<link rel='contents' href='contents.html' title="Contents" />
	9	<link rel='index' href='genindex.html' title='Index' />
	10	<link rel='last' href='about.html' title='About this document...' />
	11	<link rel='help' href='about.html' title='About this document...' />
	12	<link rel="prev" href="node794.html" />
	13	<link rel="parent" href="node792.html" />
	14	<link rel="next" href="module-compiler.visitor.html" />
	15	<meta name='aesop' content='information' />
	16	<title>19.3.3 Examples</title>
	17	</head>
	18	<body>
	19	<DIV CLASS="navigation">
	20	<div id='top-navigation-panel' xml:id='top-navigation-panel'>
	21	<table align="center" width="100%" cellpadding="0" cellspacing="2">
	22	<tr>
	23	<td class='online-navigation'><a rel="prev" title="19.3.2 Assignment nodes"
	24	href="node794.html"><img src='../icons/previous.png'
	25	border='0' height='32' alt='Previous Page' width='32' /></A></td>
	26	<td class='online-navigation'><a rel="parent" title="19.3 Python Abstract Syntax"
	27	href="node792.html"><img src='../icons/up.png'
	28	border='0' height='32' alt='Up One Level' width='32' /></A></td>
	29	<td class='online-navigation'><a rel="next" title="19.4 Using Visitors to"
	30	href="module-compiler.visitor.html"><img src='../icons/next.png'
	31	border='0' height='32' alt='Next Page' width='32' /></A></td>
	32	<td align="center" width="100%">Python Library Reference</td>
	33	<td class='online-navigation'><a rel="contents" title="Table of Contents"
	34	href="contents.html"><img src='../icons/contents.png'
	35	border='0' height='32' alt='Contents' width='32' /></A></td>
	36	<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
	37	border='0' height='32' alt='Module Index' width='32' /></a></td>
	38	<td class='online-navigation'><a rel="index" title="Index"
	39	href="genindex.html"><img src='../icons/index.png'
	40	border='0' height='32' alt='Index' width='32' /></A></td>
	41	</tr></table>
	42	<div class='online-navigation'>
	43	<b class="navlabel">Previous:</b>
	44	<a class="sectref" rel="prev" href="node794.html">19.3.2 Assignment nodes</A>
	45	<b class="navlabel">Up:</b>
	46	<a class="sectref" rel="parent" href="node792.html">19.3 Python Abstract Syntax</A>
	47	<b class="navlabel">Next:</b>
	48	<a class="sectref" rel="next" href="module-compiler.visitor.html">19.4 Using Visitors to</A>
	49	</div>
	50	<hr /></div>
	51	</DIV>
	52	<!--End of Navigation Panel-->
	53
	54	<H2><A NAME="SECTION0021330000000000000000">
	55	19.3.3 Examples</A>
	56	</H2>
	57
	58	<P>
	59	This section shows several simple examples of ASTs for Python source
	60	code. The examples demonstrate how to use the <tt class="function">parse()</tt>
	61	function, what the repr of an AST looks like, and how to access
	62	attributes of an AST node.
	63
	64	<P>
65	The first module defines a single function. Assume it is stored in
66	<span class="file">/tmp/doublelib.py</span>.
67
68	<P>
69	<div class="verbatim"><pre>
70	"""This is an example module.
71
72	This is the docstring.
73	"""
74
75	def double(x):
76	"Return twice the argument"
77	return x * 2
78	</pre></div>
79
80	<P>
81	In the interactive interpreter session below, I have reformatted the
82	long AST reprs for readability. The AST reprs use unqualified class
83	names. If you want to create an instance from a repr, you must import
84	the class names from the <tt class="module">compiler.ast</tt> module.
85
86	<P>
87	<div class="verbatim"><pre>
88	>>> import compiler
89	>>> mod = compiler.parseFile("/tmp/doublelib.py")
90	>>> mod
91	Module('This is an example module.\n\nThis is the docstring.\n',
92	Stmt([Function(None, 'double', ['x'], [], 0,
93	'Return twice the argument',
94	Stmt([Return(Mul((Name('x'), Const(2))))]))]))
95	>>> from compiler.ast import *
96	>>> Module('This is an example module.\n\nThis is the docstring.\n',
97	... Stmt([Function(None, 'double', ['x'], [], 0,
98	... 'Return twice the argument',
99	... Stmt([Return(Mul((Name('x'), Const(2))))]))]))
100	Module('This is an example module.\n\nThis is the docstring.\n',
101	Stmt([Function(None, 'double', ['x'], [], 0,
102	'Return twice the argument',
103	Stmt([Return(Mul((Name('x'), Const(2))))]))]))
104	>>> mod.doc
105	'This is an example module.\n\nThis is the docstring.\n'
106	>>> for node in mod.node.nodes:
107	... print node
108	...
109	Function(None, 'double', ['x'], [], 0, 'Return twice the argument',
110	Stmt([Return(Mul((Name('x'), Const(2))))]))
111	>>> func = mod.node.nodes[0]
112	>>> func.code
113	Stmt([Return(Mul((Name('x'), Const(2))))])
114	</pre></div>
115
116	<P>
117
118	<DIV CLASS="navigation">
119	<div class='online-navigation'>
120	<p></p><hr />
121	<table align="center" width="100%" cellpadding="0" cellspacing="2">
122	<tr>
123	<td class='online-navigation'><a rel="prev" title="19.3.2 Assignment nodes"
124	href="node794.html"><img src='../icons/previous.png'
125	border='0' height='32' alt='Previous Page' width='32' /></A></td>
126	<td class='online-navigation'><a rel="parent" title="19.3 Python Abstract Syntax"
127	href="node792.html"><img src='../icons/up.png'
128	border='0' height='32' alt='Up One Level' width='32' /></A></td>
129	<td class='online-navigation'><a rel="next" title="19.4 Using Visitors to"
130	href="module-compiler.visitor.html"><img src='../icons/next.png'
131	border='0' height='32' alt='Next Page' width='32' /></A></td>
132	<td align="center" width="100%">Python Library Reference</td>
133	<td class='online-navigation'><a rel="contents" title="Table of Contents"
134	href="contents.html"><img src='../icons/contents.png'
135	border='0' height='32' alt='Contents' width='32' /></A></td>
136	<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
137	border='0' height='32' alt='Module Index' width='32' /></a></td>
138	<td class='online-navigation'><a rel="index" title="Index"
139	href="genindex.html"><img src='../icons/index.png'
140	border='0' height='32' alt='Index' width='32' /></A></td>
141	</tr></table>
142	<div class='online-navigation'>
143	<b class="navlabel">Previous:</b>
144	<a class="sectref" rel="prev" href="node794.html">19.3.2 Assignment nodes</A>
145	<b class="navlabel">Up:</b>
146	<a class="sectref" rel="parent" href="node792.html">19.3 Python Abstract Syntax</A>
147	<b class="navlabel">Next:</b>
148	<a class="sectref" rel="next" href="module-compiler.visitor.html">19.4 Using Visitors to</A>
149	</div>
150	</div>
151	<hr />
152	<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
153	</DIV>
154	<!--End of Navigation Panel-->
155	<ADDRESS>
156	See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
157	</ADDRESS>
158	</BODY>
159	</HTML>