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="ref.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="ref.html" title='Python Reference Manual' /> | |
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="next" href="return.html" /> | |
13 | <link rel="prev" href="del.html" /> | |
14 | <link rel="parent" href="simple.html" /> | |
15 | <link rel="next" href="return.html" /> | |
16 | <meta name='aesop' content='information' /> | |
17 | <title>6.6 The print statement </title> | |
18 | </head> | |
19 | <body> | |
20 | <DIV CLASS="navigation"> | |
21 | <div id='top-navigation-panel' xml:id='top-navigation-panel'> | |
22 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
23 | <tr> | |
24 | <td class='online-navigation'><a rel="prev" title="6.5 The del statement" | |
25 | href="del.html"><img src='../icons/previous.png' | |
26 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
27 | <td class='online-navigation'><a rel="parent" title="6. Simple statements" | |
28 | href="simple.html"><img src='../icons/up.png' | |
29 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
30 | <td class='online-navigation'><a rel="next" title="6.7 The return statement" | |
31 | href="return.html"><img src='../icons/next.png' | |
32 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
33 | <td align="center" width="100%">Python Reference Manual</td> | |
34 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
35 | href="contents.html"><img src='../icons/contents.png' | |
36 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
37 | <td class='online-navigation'><img src='../icons/blank.png' | |
38 | border='0' height='32' alt='' width='32' /></td> | |
39 | <td class='online-navigation'><a rel="index" title="Index" | |
40 | href="genindex.html"><img src='../icons/index.png' | |
41 | border='0' height='32' alt='Index' width='32' /></A></td> | |
42 | </tr></table> | |
43 | <div class='online-navigation'> | |
44 | <b class="navlabel">Previous:</b> | |
45 | <a class="sectref" rel="prev" href="del.html">6.5 The del statement</A> | |
46 | <b class="navlabel">Up:</b> | |
47 | <a class="sectref" rel="parent" href="simple.html">6. Simple statements</A> | |
48 | <b class="navlabel">Next:</b> | |
49 | <a class="sectref" rel="next" href="return.html">6.7 The return statement</A> | |
50 | </div> | |
51 | <hr /></div> | |
52 | </DIV> | |
53 | <!--End of Navigation Panel--> | |
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 | ||
122 | <P> | |
123 | ||
124 | <DIV CLASS="navigation"> | |
125 | <div class='online-navigation'> | |
126 | <p></p><hr /> | |
127 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
128 | <tr> | |
129 | <td class='online-navigation'><a rel="prev" title="6.5 The del statement" | |
130 | href="del.html"><img src='../icons/previous.png' | |
131 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
132 | <td class='online-navigation'><a rel="parent" title="6. Simple statements" | |
133 | href="simple.html"><img src='../icons/up.png' | |
134 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
135 | <td class='online-navigation'><a rel="next" title="6.7 The return statement" | |
136 | href="return.html"><img src='../icons/next.png' | |
137 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
138 | <td align="center" width="100%">Python Reference Manual</td> | |
139 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
140 | href="contents.html"><img src='../icons/contents.png' | |
141 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
142 | <td class='online-navigation'><img src='../icons/blank.png' | |
143 | border='0' height='32' alt='' width='32' /></td> | |
144 | <td class='online-navigation'><a rel="index" title="Index" | |
145 | href="genindex.html"><img src='../icons/index.png' | |
146 | border='0' height='32' alt='Index' width='32' /></A></td> | |
147 | </tr></table> | |
148 | <div class='online-navigation'> | |
149 | <b class="navlabel">Previous:</b> | |
150 | <a class="sectref" rel="prev" href="del.html">6.5 The del statement</A> | |
151 | <b class="navlabel">Up:</b> | |
152 | <a class="sectref" rel="parent" href="simple.html">6. Simple statements</A> | |
153 | <b class="navlabel">Next:</b> | |
154 | <a class="sectref" rel="next" href="return.html">6.7 The return statement</A> | |
155 | </div> | |
156 | </div> | |
157 | <hr /> | |
158 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
159 | </DIV> | |
160 | <!--End of Navigation Panel--> | |
161 | <ADDRESS> | |
162 | See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. | |
163 | </ADDRESS> | |
164 | </BODY> | |
165 | </HTML> |