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| 55 | <H1><A NAME="SECTION0071800000000000000000"> |
| 56 | 5.18 <tt class="module">fileinput</tt> -- |
| 57 | Iterate over lines from multiple input streams</A> |
| 58 | </H1> |
| 59 | <A NAME="module-fileinput"></A> |
| 60 | |
| 61 | <P> |
| 62 | |
| 63 | <P> |
| 64 | This module implements a helper class and functions to quickly write a |
| 65 | loop over standard input or a list of files. |
| 66 | |
| 67 | <P> |
| 68 | The typical use is: |
| 69 | |
| 70 | <P> |
| 71 | <div class="verbatim"><pre> |
| 72 | import fileinput |
| 73 | for line in fileinput.input(): |
| 74 | process(line) |
| 75 | </pre></div> |
| 76 | |
| 77 | <P> |
| 78 | This iterates over the lines of all files listed in |
| 79 | <code>sys.argv[1:]</code>, defaulting to <code>sys.stdin</code> if the list is |
| 80 | empty. If a filename is <code>'-'</code>, it is also replaced by |
| 81 | <code>sys.stdin</code>. To specify an alternative list of filenames, pass |
| 82 | it as the first argument to <tt class="function">input()</tt>. A single file name is |
| 83 | also allowed. |
| 84 | |
| 85 | <P> |
| 86 | All files are opened in text mode. If an I/O error occurs during |
| 87 | opening or reading a file, <tt class="exception">IOError</tt> is raised. |
| 88 | |
| 89 | <P> |
| 90 | If <code>sys.stdin</code> is used more than once, the second and further use |
| 91 | will return no lines, except perhaps for interactive use, or if it has |
| 92 | been explicitly reset (e.g. using <code>sys.stdin.seek(0)</code>). |
| 93 | |
| 94 | <P> |
| 95 | Empty files are opened and immediately closed; the only time their |
| 96 | presence in the list of filenames is noticeable at all is when the |
| 97 | last file opened is empty. |
| 98 | |
| 99 | <P> |
| 100 | It is possible that the last line of a file does not end in a newline |
| 101 | character; lines are returned including the trailing newline when it |
| 102 | is present. |
| 103 | |
| 104 | <P> |
| 105 | The following function is the primary interface of this module: |
| 106 | |
| 107 | <P> |
| 108 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 109 | <td><nobr><b><tt id='l2h-1436' xml:id='l2h-1436' class="function">input</tt></b>(</nobr></td> |
| 110 | <td><var></var><big>[</big><var>files</var><big>[</big><var>, |
| 111 | inplace</var><big>[</big><var>, backup</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 112 | <dd> |
| 113 | Create an instance of the <tt class="class">FileInput</tt> class. The instance |
| 114 | will be used as global state for the functions of this module, and |
| 115 | is also returned to use during iteration. The parameters to this |
| 116 | function will be passed along to the constructor of the |
| 117 | <tt class="class">FileInput</tt> class. |
| 118 | </dl> |
| 119 | |
| 120 | <P> |
| 121 | The following functions use the global state created by |
| 122 | <tt class="function">input()</tt>; if there is no active state, |
| 123 | <tt class="exception">RuntimeError</tt> is raised. |
| 124 | |
| 125 | <P> |
| 126 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 127 | <td><nobr><b><tt id='l2h-1437' xml:id='l2h-1437' class="function">filename</tt></b>(</nobr></td> |
| 128 | <td><var></var>)</td></tr></table></dt> |
| 129 | <dd> |
| 130 | Return the name of the file currently being read. Before the first |
| 131 | line has been read, returns <code>None</code>. |
| 132 | </dl> |
| 133 | |
| 134 | <P> |
| 135 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 136 | <td><nobr><b><tt id='l2h-1438' xml:id='l2h-1438' class="function">lineno</tt></b>(</nobr></td> |
| 137 | <td><var></var>)</td></tr></table></dt> |
| 138 | <dd> |
| 139 | Return the cumulative line number of the line that has just been |
| 140 | read. Before the first line has been read, returns <code>0</code>. After |
| 141 | the last line of the last file has been read, returns the line |
| 142 | number of that line. |
| 143 | </dl> |
| 144 | |
| 145 | <P> |
| 146 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 147 | <td><nobr><b><tt id='l2h-1439' xml:id='l2h-1439' class="function">filelineno</tt></b>(</nobr></td> |
| 148 | <td><var></var>)</td></tr></table></dt> |
| 149 | <dd> |
| 150 | Return the line number in the current file. Before the first line |
| 151 | has been read, returns <code>0</code>. After the last line of the last |
| 152 | file has been read, returns the line number of that line within the |
| 153 | file. |
| 154 | </dl> |
| 155 | |
| 156 | <P> |
| 157 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 158 | <td><nobr><b><tt id='l2h-1440' xml:id='l2h-1440' class="function">isfirstline</tt></b>(</nobr></td> |
| 159 | <td><var></var>)</td></tr></table></dt> |
| 160 | <dd> |
| 161 | Returns true if the line just read is the first line of its file, |
| 162 | otherwise returns false. |
| 163 | </dl> |
| 164 | |
| 165 | <P> |
| 166 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 167 | <td><nobr><b><tt id='l2h-1441' xml:id='l2h-1441' class="function">isstdin</tt></b>(</nobr></td> |
| 168 | <td><var></var>)</td></tr></table></dt> |
| 169 | <dd> |
| 170 | Returns true if the last line was read from <code>sys.stdin</code>, |
| 171 | otherwise returns false. |
| 172 | </dl> |
| 173 | |
| 174 | <P> |
| 175 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 176 | <td><nobr><b><tt id='l2h-1442' xml:id='l2h-1442' class="function">nextfile</tt></b>(</nobr></td> |
| 177 | <td><var></var>)</td></tr></table></dt> |
| 178 | <dd> |
| 179 | Close the current file so that the next iteration will read the |
| 180 | first line from the next file (if any); lines not read from the file |
| 181 | will not count towards the cumulative line count. The filename is |
| 182 | not changed until after the first line of the next file has been |
| 183 | read. Before the first line has been read, this function has no |
| 184 | effect; it cannot be used to skip the first file. After the last |
| 185 | line of the last file has been read, this function has no effect. |
| 186 | </dl> |
| 187 | |
| 188 | <P> |
| 189 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 190 | <td><nobr><b><tt id='l2h-1443' xml:id='l2h-1443' class="function">close</tt></b>(</nobr></td> |
| 191 | <td><var></var>)</td></tr></table></dt> |
| 192 | <dd> |
| 193 | Close the sequence. |
| 194 | </dl> |
| 195 | |
| 196 | <P> |
| 197 | The class which implements the sequence behavior provided by the |
| 198 | module is available for subclassing as well: |
| 199 | |
| 200 | <P> |
| 201 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 202 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-1444' xml:id='l2h-1444' class="class">FileInput</tt></b>(</nobr></td> |
| 203 | <td><var></var><big>[</big><var>files</var><big>[</big><var>, |
| 204 | inplace</var><big>[</big><var>, backup</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 205 | <dd> |
| 206 | Class <tt class="class">FileInput</tt> is the implementation; its methods |
| 207 | <tt class="method">filename()</tt>, <tt class="method">lineno()</tt>, <tt class="method">fileline()</tt>, |
| 208 | <tt class="method">isfirstline()</tt>, <tt class="method">isstdin()</tt>, <tt class="method">nextfile()</tt> and |
| 209 | <tt class="method">close()</tt> correspond to the functions of the same name in the |
| 210 | module. In addition it has a <tt class="method">readline()</tt> method which |
| 211 | returns the next input line, and a <tt class="method">__getitem__()</tt> method |
| 212 | which implements the sequence behavior. The sequence must be |
| 213 | accessed in strictly sequential order; random access and |
| 214 | <tt class="method">readline()</tt> cannot be mixed. |
| 215 | </dl> |
| 216 | |
| 217 | <P> |
| 218 | <strong>Optional in-place filtering:</strong> if the keyword argument |
| 219 | <code><var>inplace</var>=1</code> is passed to <tt class="function">input()</tt> or to the |
| 220 | <tt class="class">FileInput</tt> constructor, the file is moved to a backup file and |
| 221 | standard output is directed to the input file (if a file of the same |
| 222 | name as the backup file already exists, it will be replaced silently). |
| 223 | This makes it possible to write a filter that rewrites its input file |
| 224 | in place. If the keyword argument <code><var>backup</var>='.<some |
| 225 | extension>'</code> is also given, it specifies the extension for the backup |
| 226 | file, and the backup file remains around; by default, the extension is |
| 227 | <code>'.bak'</code> and it is deleted when the output file is closed. In-place |
| 228 | filtering is disabled when standard input is read. |
| 229 | |
| 230 | <P> |
| 231 | <strong>Caveat:</strong> The current implementation does not work for MS-DOS |
| 232 | 8+3 filesystems. |
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