projects / OpenSPARC-T2-DV / blame
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| 53 | ||
| 54 | <H2><A NAME="SECTION007270000000000000000"></A><A NAME="string-conversions"></A> | |
| 55 | <BR> | |
| 56 | 5.2.7 String conversions | |
| 57 | </H2> | |
| 58 | <a id='l2h-356' xml:id='l2h-356'></a><a id='l2h-357' xml:id='l2h-357'></a><a id='l2h-358' xml:id='l2h-358'></a><a id='l2h-362' xml:id='l2h-362'></a> | |
| 59 | ||
| 60 | <P> | |
| 61 | A string conversion is an expression list enclosed in reverse (a.k.a. | |
| 62 | backward) quotes: | |
| 63 | ||
| 64 | <P> | |
| 65 | <dl><dd class="grammar"> | |
| 66 | <div class="productions"> | |
| 67 | <table> | |
| 68 | <tr> | |
| 69 | <td><a id='tok-string_conversion' xml:id='tok-string_conversion'>string_conversion</a></td> | |
| 70 | <td>::=</td> | |
| 71 | <td>"`" <a class='grammartoken' href="exprlists.html#tok-expression_list">expression_list</a> "`"</td></tr> | |
| 72 | </table> | |
| 73 | </div> | |
| 74 | <a class="grammar-footer" | |
| 75 | href="grammar.txt" type="text/plain" | |
| 76 | >Download entire grammar as text.</a> | |
| 77 | </dd></dl> | |
| 78 | ||
| 79 | <P> | |
| 80 | A string conversion evaluates the contained expression list and | |
| 81 | converts the resulting object into a string according to rules | |
| 82 | specific to its type. | |
| 83 | ||
| 84 | <P> | |
| 85 | If the object is a string, a number, <code>None</code>, or a tuple, list or | |
| 86 | dictionary containing only objects whose type is one of these, the | |
| 87 | resulting string is a valid Python expression which can be passed to | |
| 88 | the built-in function <tt class="function">eval()</tt> to yield an expression with the | |
| 89 | same value (or an approximation, if floating point numbers are | |
| 90 | involved). | |
| 91 | ||
| 92 | <P> | |
| 93 | (In particular, converting a string adds quotes around it and converts | |
| 94 | ``funny'' characters to escape sequences that are safe to print.) | |
| 95 | ||
| 96 | <P> | |
| 97 | Recursive objects (for example, lists or dictionaries that contain a | |
| 98 | reference to themselves, directly or indirectly) use "<tt class="samp">...</tt>" to | |
| 99 | indicate a recursive reference, and the result cannot be passed to | |
| 100 | <tt class="function">eval()</tt> to get an equal value (<tt class="exception">SyntaxError</tt> will | |
| 101 | be raised instead). | |
| 102 | <a id='l2h-359' xml:id='l2h-359'></a> | |
| 103 | <P> | |
| 104 | The built-in function <tt class="function">repr()</tt> performs exactly the same | |
| 105 | conversion in its argument as enclosing it in parentheses and reverse | |
| 106 | quotes does. The built-in function <tt class="function">str()</tt> performs a | |
| 107 | similar but more user-friendly conversion. | |
| 108 | <a id='l2h-360' xml:id='l2h-360'></a><a id='l2h-361' xml:id='l2h-361'></a> | |
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| 145 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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