projects / OpenSPARC-T2-DV / blame
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| 54 | ||
| 55 | <H1><A NAME="SECTION008600000000000000000"></A><A NAME="print"></A> | |
| 56 | <BR> | |
| 57 | 6.6 The <tt class="keyword">print</tt> statement | |
| 58 | </H1> | |
| 59 | <a id='l2h-495' xml:id='l2h-495'></a> | |
| 60 | <P> | |
| 61 | <dl><dd class="grammar"> | |
| 62 | <div class="productions"> | |
| 63 | <table> | |
| 64 | <tr> | |
| 65 | <td><a id='tok-print_stmt' xml:id='tok-print_stmt'>print_stmt</a></td> | |
| 66 | <td>::=</td> | |
| 67 | <td>"print" ( <big>[</big><a class='grammartoken' href="Booleans.html#tok-expression">expression</a> ("," <a class='grammartoken' href="Booleans.html#tok-expression">expression</a>)* <big>[</big>","<big>]</big><big>]</big></td></tr> | |
| 68 | <tr> | |
| 69 | <td></td> | |
| 70 | <td></td> | |
| 71 | <td><code>| "><code>></code>" <a class='grammartoken' href="Booleans.html#tok-expression">expression</a> | |
| 72 | <big>[</big>("," <a class='grammartoken' href="Booleans.html#tok-expression">expression</a>)+ <big>[</big>","<big>]</big><big>]</big> )</code></td></tr> | |
| 73 | </table> | |
| 74 | </div> | |
| 75 | <a class="grammar-footer" | |
| 76 | href="grammar.txt" type="text/plain" | |
| 77 | >Download entire grammar as text.</a> | |
| 78 | </dd></dl> | |
| 79 | ||
| 80 | <P> | |
| 81 | <tt class="keyword">print</tt> evaluates each expression in turn and writes the | |
| 82 | resulting object to standard output (see below). If an object is not | |
| 83 | a string, it is first converted to a string using the rules for string | |
| 84 | conversions. The (resulting or original) string is then written. A | |
| 85 | space is written before each object is (converted and) written, unless | |
| 86 | the output system believes it is positioned at the beginning of a | |
| 87 | line. This is the case (1) when no characters have yet been written | |
| 88 | to standard output, (2) when the last character written to standard | |
| 89 | output is "<tt class="character">\n</tt>", or (3) when the last write operation on | |
| 90 | standard output was not a <tt class="keyword">print</tt> statement. (In some cases | |
| 91 | it may be functional to write an empty string to standard output for | |
| 92 | this reason.) <span class="note"><b class="label">Note:</b> | |
| 93 | Objects which act like file objects but which are | |
| 94 | not the built-in file objects often do not properly emulate this | |
| 95 | aspect of the file object's behavior, so it is best not to rely on | |
| 96 | this.</span> | |
| 97 | <a id='l2h-503' xml:id='l2h-503'></a> | |
| 98 | <a id='l2h-496' xml:id='l2h-496'></a> | |
| 99 | <P> | |
| 100 | A "<tt class="character">\n</tt>" character is written at the end, unless the | |
| 101 | <tt class="keyword">print</tt> statement ends with a comma. This is the only action | |
| 102 | if the statement contains just the keyword <tt class="keyword">print</tt>. | |
| 103 | <a id='l2h-497' xml:id='l2h-497'></a><a id='l2h-498' xml:id='l2h-498'></a> | |
| 104 | <P> | |
| 105 | Standard output is defined as the file object named <code>stdout</code> | |
| 106 | in the built-in module <tt class="module">sys</tt>. If no such object exists, or if | |
| 107 | it does not have a <tt class="method">write()</tt> method, a <tt class="exception">RuntimeError</tt> | |
| 108 | exception is raised. | |
| 109 | <a id='l2h-499' xml:id='l2h-499'></a><a id='l2h-504' xml:id='l2h-504'></a> | |
| 110 | <a id='l2h-501' xml:id='l2h-501'></a><a id='l2h-502' xml:id='l2h-502'></a> | |
| 111 | <P> | |
| 112 | <tt class="keyword">print</tt> also has an extended<a id='l2h-505' xml:id='l2h-505'></a> | |
| 113 | form, defined by the second portion of the syntax described above. | |
| 114 | This form is sometimes referred to as ``<tt class="keyword">print</tt> chevron.'' | |
| 115 | In this form, the first expression after the <code>></code><code>></code> must | |
| 116 | evaluate to a ``file-like'' object, specifically an object that has a | |
| 117 | <tt class="method">write()</tt> method as described above. With this extended form, | |
| 118 | the subsequent expressions are printed to this file object. If the | |
| 119 | first expression evaluates to <code>None</code>, then <code>sys.stdout</code> is | |
| 120 | used as the file for output. | |
| 121 | ||
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| 158 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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