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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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