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| 53 | <H1><A NAME="SECTION00102300000000000000000"> |
| 54 | 10.23 <tt class="module">distutils.text_file</tt> -- The TextFile class</A> |
| 55 | </H1> |
| 56 | <A NAME="module-distutils.textfile"></A> |
| 57 | |
| 58 | <P> |
| 59 | This module provides the <tt class="class">TextFile</tt> class, which gives an interface |
| 60 | to text files that (optionally) takes care of stripping comments, ignoring |
| 61 | blank lines, and joining lines with backslashes. |
| 62 | |
| 63 | <P> |
| 64 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 65 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-118' xml:id='l2h-118' class="class">TextFile</tt></b>(</nobr></td> |
| 66 | <td><var></var><big>[</big><var>filename=<code>None</code>, file=<code>None</code>, **options</var><big>]</big><var></var>)</td></tr></table></dt> |
| 67 | <dd> |
| 68 | This class provides a file-like object that takes care of all |
| 69 | the things you commonly want to do when processing a text file |
| 70 | that has some line-by-line syntax: strip comments (as long as <code>#</code> |
| 71 | is your comment character), skip blank lines, join adjacent lines by |
| 72 | escaping the newline (ie. backslash at end of line), strip |
| 73 | leading and/or trailing whitespace. All of these are optional |
| 74 | and independently controllable. |
| 75 | |
| 76 | <P> |
| 77 | The class provides a <tt class="method">warn()</tt> method so you can generate |
| 78 | warning messages that report physical line number, even if the |
| 79 | logical line in question spans multiple physical lines. Also |
| 80 | provides <tt class="method">unreadline()</tt> for implementing line-at-a-time lookahead. |
| 81 | |
| 82 | <P> |
| 83 | <tt class="class">TextFile</tt> instances are create with either <var>filename</var>, <var>file</var>, |
| 84 | or both. <tt class="exception">RuntimeError</tt> is raised if both are <code>None</code>. |
| 85 | <var>filename</var> should be a string, and <var>file</var> a file object (or |
| 86 | something that provides <tt class="method">readline()</tt> and <tt class="method">close()</tt> |
| 87 | methods). It is recommended that you supply at least <var>filename</var>, |
| 88 | so that <tt class="class">TextFile</tt> can include it in warning messages. If |
| 89 | <var>file</var> is not supplied, <tt class="class">TextFile</tt> creates its own using the |
| 90 | <tt class="function">open()</tt> built-in function. |
| 91 | |
| 92 | <P> |
| 93 | The options are all boolean, and affect the values returned by |
| 94 | <tt class="method">readline()</tt> |
| 95 | |
| 96 | <P> |
| 97 | <div class="center"><table class="realtable"> |
| 98 | <thead> |
| 99 | <tr> |
| 100 | <th class="center">option name</th> |
| 101 | <th class="left" >description</th> |
| 102 | <th class="left" >default</th> |
| 103 | </tr> |
| 104 | </thead> |
| 105 | <tbody> |
| 106 | <tr><td class="center" valign="baseline"><option name>strip_comments</option></td> |
| 107 | <td class="left" > |
| 108 | strip from "<tt class="character">#</tt>" to end-of-line, as well as any whitespace |
| 109 | leading up to the "<tt class="character">#</tt>"--unless it is escaped by a backslash</td> |
| 110 | <td class="left" >true</td></tr> |
| 111 | <tr><td class="center" valign="baseline"><option name>lstrip_ws</option></td> |
| 112 | <td class="left" > |
| 113 | strip leading whitespace from each line before returning it</td> |
| 114 | <td class="left" >false</td></tr> |
| 115 | <tr><td class="center" valign="baseline"><option name>rstrip_ws</option></td> |
| 116 | <td class="left" > |
| 117 | strip trailing whitespace (including line terminator!) from |
| 118 | each line before returning it.</td> |
| 119 | <td class="left" >true</td></tr> |
| 120 | <tr><td class="center" valign="baseline"><option name>skip_blanks</option></td> |
| 121 | <td class="left" > |
| 122 | skip lines that are empty *after* stripping comments and |
| 123 | whitespace. (If both lstrip_ws and rstrip_ws are false, |
| 124 | then some lines may consist of solely whitespace: these will |
| 125 | *not* be skipped, even if <var>skip_blanks</var> is true.)</td> |
| 126 | <td class="left" >true</td></tr> |
| 127 | <tr><td class="center" valign="baseline"><option name>join_lines</option></td> |
| 128 | <td class="left" > |
| 129 | if a backslash is the last non-newline character on a line |
| 130 | after stripping comments and whitespace, join the following line |
| 131 | to it to form one logical line; if N consecutive lines end |
| 132 | with a backslash, then N+1 physical lines will be joined to |
| 133 | form one logical line.</td> |
| 134 | <td class="left" >false</td></tr> |
| 135 | <tr><td class="center" valign="baseline"><option name>collapse_join</option></td> |
| 136 | <td class="left" > |
| 137 | strip leading whitespace from lines that are joined to their |
| 138 | predecessor; only matters if "<tt class="samp">(join_lines and not lstrip_ws)</tt>"</td> |
| 139 | <td class="left" >false</td></tr></tbody> |
| 140 | </table></div> |
| 141 | |
| 142 | <P> |
| 143 | Note that since <var>rstrip_ws</var> can strip the trailing newline, the |
| 144 | semantics of <tt class="method">readline()</tt> must differ from those of the builtin file |
| 145 | object's <tt class="method">readline()</tt> method! In particular, <tt class="method">readline()</tt> |
| 146 | returns <code>None</code> for end-of-file: an empty string might just be a |
| 147 | blank line (or an all-whitespace line), if <var>rstrip_ws</var> is true |
| 148 | but <var>skip_blanks</var> is not. |
| 149 | |
| 150 | <P> |
| 151 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 152 | <td><nobr><b><tt id='l2h-119' xml:id='l2h-119' class="method">open</tt></b>(</nobr></td> |
| 153 | <td><var>filename</var>)</td></tr></table></dt> |
| 154 | <dd> |
| 155 | Open a new file <var>filename</var>. This overrides any <var>file</var> or |
| 156 | <var>filename</var> constructor arguments. |
| 157 | </dl> |
| 158 | |
| 159 | <P> |
| 160 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 161 | <td><nobr><b><tt id='l2h-120' xml:id='l2h-120' class="method">close</tt></b>(</nobr></td> |
| 162 | <td><var></var>)</td></tr></table></dt> |
| 163 | <dd> |
| 164 | Close the current file and forget everything we know about it (including |
| 165 | the filename and the current line number). |
| 166 | </dl> |
| 167 | |
| 168 | <P> |
| 169 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 170 | <td><nobr><b><tt id='l2h-121' xml:id='l2h-121' class="method">warn</tt></b>(</nobr></td> |
| 171 | <td><var>msg</var><big>[</big><var>,line=<code>None</code></var><big>]</big><var></var>)</td></tr></table></dt> |
| 172 | <dd> |
| 173 | Print (to stderr) a warning message tied to the current logical |
| 174 | line in the current file. If the current logical line in the |
| 175 | file spans multiple physical lines, the warning refers to the |
| 176 | whole range, such as "<tt class="samp">"lines 3-5"</tt>". If <var>line</var> is supplied, |
| 177 | it overrides the current line number; it may be a list or tuple |
| 178 | to indicate a range of physical lines, or an integer for a |
| 179 | single physical line. |
| 180 | </dl> |
| 181 | |
| 182 | <P> |
| 183 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 184 | <td><nobr><b><tt id='l2h-122' xml:id='l2h-122' class="method">readline</tt></b>(</nobr></td> |
| 185 | <td><var></var>)</td></tr></table></dt> |
| 186 | <dd> |
| 187 | Read and return a single logical line from the current file (or |
| 188 | from an internal buffer if lines have previously been ``unread'' |
| 189 | with <tt class="method">unreadline()</tt>). If the <var>join_lines</var> option |
| 190 | is true, this may involve reading multiple physical lines |
| 191 | concatenated into a single string. Updates the current line number, |
| 192 | so calling <tt class="method">warn()</tt> after <tt class="method">readline()</tt> emits a warning |
| 193 | about the physical line(s) just read. Returns <code>None</code> on end-of-file, |
| 194 | since the empty string can occur if <var>rstrip_ws</var> is true but |
| 195 | <var>strip_blanks</var> is not. |
| 196 | </dl> |
| 197 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 198 | <td><nobr><b><tt id='l2h-123' xml:id='l2h-123' class="method">readlines</tt></b>(</nobr></td> |
| 199 | <td><var></var>)</td></tr></table></dt> |
| 200 | <dd> |
| 201 | Read and return the list of all logical lines remaining in the current file. |
| 202 | This updates the current line number to the last line of the file. |
| 203 | </dl> |
| 204 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 205 | <td><nobr><b><tt id='l2h-124' xml:id='l2h-124' class="method">unreadline</tt></b>(</nobr></td> |
| 206 | <td><var>line</var>)</td></tr></table></dt> |
| 207 | <dd> |
| 208 | Push <var>line</var> (a string) onto an internal buffer that will be |
| 209 | checked by future <tt class="method">readline()</tt> calls. Handy for implementing |
| 210 | a parser with line-at-a-time lookahead. Note that lines that are ``unread'' |
| 211 | with <tt class="method">unreadline</tt> are not subsequently re-cleansed (whitespace |
| 212 | stripped, or whatever) when read with <tt class="method">readline</tt>. If multiple |
| 213 | calls are made to <tt class="method">unreadline</tt> before a call to <tt class="method">readline</tt>, |
| 214 | the lines will be returned most in most recent first order. |
| 215 | </dl> |
| 216 | |
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| 218 | </dl> |
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