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55 | <H3><A NAME="SECTION0020161000000000000000"> | |
56 | 18.1.6.1 Emulation of <tt class="function">compile()</tt></A> | |
57 | </H3> | |
58 | ||
59 | <P> | |
60 | While many useful operations may take place between parsing and | |
61 | bytecode generation, the simplest operation is to do nothing. For | |
62 | this purpose, using the <tt class="module">parser</tt> module to produce an | |
63 | intermediate data structure is equivalent to the code | |
64 | ||
65 | <P> | |
66 | <div class="verbatim"><pre> | |
67 | >>> code = compile('a + 5', 'file.py', 'eval') | |
68 | >>> a = 5 | |
69 | >>> eval(code) | |
70 | 10 | |
71 | </pre></div> | |
72 | ||
73 | <P> | |
74 | The equivalent operation using the <tt class="module">parser</tt> module is somewhat | |
75 | longer, and allows the intermediate internal parse tree to be retained | |
76 | as an AST object: | |
77 | ||
78 | <P> | |
79 | <div class="verbatim"><pre> | |
80 | >>> import parser | |
81 | >>> ast = parser.expr('a + 5') | |
82 | >>> code = ast.compile('file.py') | |
83 | >>> a = 5 | |
84 | >>> eval(code) | |
85 | 10 | |
86 | </pre></div> | |
87 | ||
88 | <P> | |
89 | An application which needs both AST and code objects can package this | |
90 | code into readily available functions: | |
91 | ||
92 | <P> | |
93 | <div class="verbatim"><pre> | |
94 | import parser | |
95 | ||
96 | def load_suite(source_string): | |
97 | ast = parser.suite(source_string) | |
98 | return ast, ast.compile() | |
99 | ||
100 | def load_expression(source_string): | |
101 | ast = parser.expr(source_string) | |
102 | return ast, ast.compile() | |
103 | </pre></div> | |
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