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="lib.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="lib.html" title='Python Library Reference' /> | |
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="stream-reader-writer.html" /> | |
13 | <link rel="prev" href="stream-writer-objects.html" /> | |
14 | <link rel="parent" href="node130.html" /> | |
15 | <link rel="next" href="stream-reader-writer.html" /> | |
16 | <meta name='aesop' content='information' /> | |
17 | <title>4.9.1.3 StreamReader Objects </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="4.9.1.2 StreamWriter Objects" | |
25 | href="stream-writer-objects.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="4.9.1 Codec Base Classes" | |
28 | href="node130.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="4.9.1.4 StreamReaderWriter Objects" | |
31 | href="stream-reader-writer.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 Library Reference</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'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' | |
38 | border='0' height='32' alt='Module Index' width='32' /></a></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="stream-writer-objects.html">4.9.1.2 StreamWriter Objects</A> | |
46 | <b class="navlabel">Up:</b> | |
47 | <a class="sectref" rel="parent" href="node130.html">4.9.1 Codec Base Classes</A> | |
48 | <b class="navlabel">Next:</b> | |
49 | <a class="sectref" rel="next" href="stream-reader-writer.html">4.9.1.4 StreamReaderWriter Objects</A> | |
50 | </div> | |
51 | <hr /></div> | |
52 | </DIV> | |
53 | <!--End of Navigation Panel--> | |
54 | ||
55 | <H3><A NAME="SECTION006913000000000000000"></A><A NAME="stream-reader-objects"></A> | |
56 | <BR> | |
57 | 4.9.1.3 StreamReader Objects | |
58 | </H3> | |
59 | ||
60 | <P> | |
61 | The <tt class="class">StreamReader</tt> class is a subclass of <tt class="class">Codec</tt> and | |
62 | defines the following methods which every stream reader must define in | |
63 | order to be compatible to the Python codec registry. | |
64 | ||
65 | <P> | |
66 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
67 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-1011' xml:id='l2h-1011' class="class">StreamReader</tt></b>(</nobr></td> | |
68 | <td><var>stream</var><big>[</big><var>, errors</var><big>]</big><var></var>)</td></tr></table></dt> | |
69 | <dd> | |
70 | Constructor for a <tt class="class">StreamReader</tt> instance. | |
71 | ||
72 | <P> | |
73 | All stream readers must provide this constructor interface. They are | |
74 | free to add additional keyword arguments, but only the ones defined | |
75 | here are used by the Python codec registry. | |
76 | ||
77 | <P> | |
78 | <var>stream</var> must be a file-like object open for reading (binary) | |
79 | data. | |
80 | ||
81 | <P> | |
82 | The <tt class="class">StreamReader</tt> may implement different error handling | |
83 | schemes by providing the <var>errors</var> keyword argument. These | |
84 | parameters are defined: | |
85 | ||
86 | <P> | |
87 | ||
88 | <UL> | |
89 | <LI><code>'strict'</code> Raise <tt class="exception">ValueError</tt> (or a subclass); | |
90 | this is the default. | |
91 | </LI> | |
92 | <LI><code>'ignore'</code> Ignore the character and continue with the next. | |
93 | </LI> | |
94 | <LI><code>'replace'</code> Replace with a suitable replacement character. | |
95 | ||
96 | </LI> | |
97 | </UL> | |
98 | ||
99 | <P> | |
100 | The <var>errors</var> argument will be assigned to an attribute of the | |
101 | same name. Assigning to this attribute makes it possible to switch | |
102 | between different error handling strategies during the lifetime | |
103 | of the <tt class="class">StreamReader</tt> object. | |
104 | ||
105 | <P> | |
106 | The set of allowed values for the <var>errors</var> argument can | |
107 | be extended with <tt class="function">register_error()</tt>. | |
108 | </dl> | |
109 | ||
110 | <P> | |
111 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
112 | <td><nobr><b><tt id='l2h-1012' xml:id='l2h-1012' class="method">read</tt></b>(</nobr></td> | |
113 | <td><var></var><big>[</big><var>size</var><big>[</big><var>, chars, </var><big>[</big><var>firstline</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> | |
114 | <dd> | |
115 | Decodes data from the stream and returns the resulting object. | |
116 | ||
117 | <P> | |
118 | <var>chars</var> indicates the number of characters to read from the | |
119 | stream. <tt class="function">read()</tt> will never return more than <var>chars</var> | |
120 | characters, but it might return less, if there are not enough | |
121 | characters available. | |
122 | ||
123 | <P> | |
124 | <var>size</var> indicates the approximate maximum number of bytes to read | |
125 | from the stream for decoding purposes. The decoder can modify this | |
126 | setting as appropriate. The default value -1 indicates to read and | |
127 | decode as much as possible. <var>size</var> is intended to prevent having | |
128 | to decode huge files in one step. | |
129 | ||
130 | <P> | |
131 | <var>firstline</var> indicates that it would be sufficient to only return | |
132 | the first line, if there are decoding errors on later lines. | |
133 | ||
134 | <P> | |
135 | The method should use a greedy read strategy meaning that it should | |
136 | read as much data as is allowed within the definition of the encoding | |
137 | and the given size, e.g. if optional encoding endings or state | |
138 | markers are available on the stream, these should be read too. | |
139 | ||
140 | <P> | |
141 | ||
142 | <span class="versionnote">Changed in version 2.4: | |
143 | <var>chars</var> argument added.</span> | |
144 | ||
145 | <span class="versionnote">Changed in version 2.4.2: | |
146 | <var>firstline</var> argument added.</span> | |
147 | ||
148 | </dl> | |
149 | ||
150 | <P> | |
151 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
152 | <td><nobr><b><tt id='l2h-1013' xml:id='l2h-1013' class="method">readline</tt></b>(</nobr></td> | |
153 | <td><var></var><big>[</big><var>size</var><big>[</big><var>, keepends</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> | |
154 | <dd> | |
155 | Read one line from the input stream and return the | |
156 | decoded data. | |
157 | ||
158 | <P> | |
159 | <var>size</var>, if given, is passed as size argument to the stream's | |
160 | <tt class="method">readline()</tt> method. | |
161 | ||
162 | <P> | |
163 | If <var>keepends</var> is false lineends will be stripped from the | |
164 | lines returned. | |
165 | ||
166 | <P> | |
167 | ||
168 | <span class="versionnote">Changed in version 2.4: | |
169 | <var>keepends</var> argument added.</span> | |
170 | ||
171 | </dl> | |
172 | ||
173 | <P> | |
174 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
175 | <td><nobr><b><tt id='l2h-1014' xml:id='l2h-1014' class="method">readlines</tt></b>(</nobr></td> | |
176 | <td><var></var><big>[</big><var>sizehint</var><big>[</big><var>, keepends</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> | |
177 | <dd> | |
178 | Read all lines available on the input stream and return them as list | |
179 | of lines. | |
180 | ||
181 | <P> | |
182 | Line breaks are implemented using the codec's decoder method and are | |
183 | included in the list entries if <var>keepends</var> is true. | |
184 | ||
185 | <P> | |
186 | <var>sizehint</var>, if given, is passed as <var>size</var> argument to the | |
187 | stream's <tt class="method">read()</tt> method. | |
188 | </dl> | |
189 | ||
190 | <P> | |
191 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
192 | <td><nobr><b><tt id='l2h-1015' xml:id='l2h-1015' class="method">reset</tt></b>(</nobr></td> | |
193 | <td><var></var>)</td></tr></table></dt> | |
194 | <dd> | |
195 | Resets the codec buffers used for keeping state. | |
196 | ||
197 | <P> | |
198 | Note that no stream repositioning should take place. This method is | |
199 | primarily intended to be able to recover from decoding errors. | |
200 | </dl> | |
201 | ||
202 | <P> | |
203 | In addition to the above methods, the <tt class="class">StreamReader</tt> must also | |
204 | inherit all other methods and attribute from the underlying stream. | |
205 | ||
206 | <P> | |
207 | The next two base classes are included for convenience. They are not | |
208 | needed by the codec registry, but may provide useful in practice. | |
209 | ||
210 | <P> | |
211 | ||
212 | <DIV CLASS="navigation"> | |
213 | <div class='online-navigation'> | |
214 | <p></p><hr /> | |
215 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
216 | <tr> | |
217 | <td class='online-navigation'><a rel="prev" title="4.9.1.2 StreamWriter Objects" | |
218 | href="stream-writer-objects.html"><img src='../icons/previous.png' | |
219 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
220 | <td class='online-navigation'><a rel="parent" title="4.9.1 Codec Base Classes" | |
221 | href="node130.html"><img src='../icons/up.png' | |
222 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
223 | <td class='online-navigation'><a rel="next" title="4.9.1.4 StreamReaderWriter Objects" | |
224 | href="stream-reader-writer.html"><img src='../icons/next.png' | |
225 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
226 | <td align="center" width="100%">Python Library Reference</td> | |
227 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
228 | href="contents.html"><img src='../icons/contents.png' | |
229 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
230 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' | |
231 | border='0' height='32' alt='Module Index' width='32' /></a></td> | |
232 | <td class='online-navigation'><a rel="index" title="Index" | |
233 | href="genindex.html"><img src='../icons/index.png' | |
234 | border='0' height='32' alt='Index' width='32' /></A></td> | |
235 | </tr></table> | |
236 | <div class='online-navigation'> | |
237 | <b class="navlabel">Previous:</b> | |
238 | <a class="sectref" rel="prev" href="stream-writer-objects.html">4.9.1.2 StreamWriter Objects</A> | |
239 | <b class="navlabel">Up:</b> | |
240 | <a class="sectref" rel="parent" href="node130.html">4.9.1 Codec Base Classes</A> | |
241 | <b class="navlabel">Next:</b> | |
242 | <a class="sectref" rel="next" href="stream-reader-writer.html">4.9.1.4 StreamReaderWriter Objects</A> | |
243 | </div> | |
244 | </div> | |
245 | <hr /> | |
246 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
247 | </DIV> | |
248 | <!--End of Navigation Panel--> | |
249 | <ADDRESS> | |
250 | See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. | |
251 | </ADDRESS> | |
252 | </BODY> | |
253 | </HTML> |