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| 55 | <H2><A NAME="SECTION0082820000000000000000"> |
| 56 | 6.28.2 Class-based API</A> |
| 57 | </H2> |
| 58 | |
| 59 | <P> |
| 60 | The class-based API of the <tt class="module">gettext</tt> module gives you more |
| 61 | flexibility and greater convenience than the GNU <b class="program">gettext</b> |
| 62 | API. It is the recommended way of localizing your Python applications and |
| 63 | modules. <tt class="module">gettext</tt> defines a ``translations'' class which |
| 64 | implements the parsing of GNU <span class="file">.mo</span> format files, and has methods |
| 65 | for returning either standard 8-bit strings or Unicode strings. |
| 66 | Instances of this ``translations'' class can also install themselves |
| 67 | in the built-in namespace as the function <tt class="function">_()</tt>. |
| 68 | |
| 69 | <P> |
| 70 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 71 | <td><nobr><b><tt id='l2h-2427' xml:id='l2h-2427' class="function">find</tt></b>(</nobr></td> |
| 72 | <td><var>domain</var><big>[</big><var>, localedir</var><big>[</big><var>, |
| 73 | languages</var><big>[</big><var>, all</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 74 | <dd> |
| 75 | This function implements the standard <span class="file">.mo</span> file search |
| 76 | algorithm. It takes a <var>domain</var>, identical to what |
| 77 | <tt class="function">textdomain()</tt> takes. Optional <var>localedir</var> is as in |
| 78 | <tt class="function">bindtextdomain()</tt> Optional <var>languages</var> is a list of |
| 79 | strings, where each string is a language code. |
| 80 | |
| 81 | <P> |
| 82 | If <var>localedir</var> is not given, then the default system locale |
| 83 | directory is used.<A NAME="tex2html43" |
| 84 | HREF="#foot36704"><SUP>6.3</SUP></A> If <var>languages</var> is not given, |
| 85 | then the following environment variables are searched: <a class="envvar" id='l2h-2430' xml:id='l2h-2430'>LANGUAGE</a>, |
| 86 | <a class="envvar" id='l2h-2431' xml:id='l2h-2431'>LC_ALL</a>, <a class="envvar" id='l2h-2432' xml:id='l2h-2432'>LC_MESSAGES</a>, and <a class="envvar" id='l2h-2433' xml:id='l2h-2433'>LANG</a>. The first one |
| 87 | returning a non-empty value is used for the <var>languages</var> variable. |
| 88 | The environment variables should contain a colon separated list of |
| 89 | languages, which will be split on the colon to produce the expected |
| 90 | list of language code strings. |
| 91 | |
| 92 | <P> |
| 93 | <tt class="function">find()</tt> then expands and normalizes the languages, and then |
| 94 | iterates through them, searching for an existing file built of these |
| 95 | components: |
| 96 | |
| 97 | <P> |
| 98 | <span class="file"><var>localedir</var>/<var>language</var>/LC_MESSAGES/<var>domain</var>.mo</span> |
| 99 | |
| 100 | <P> |
| 101 | The first such file name that exists is returned by <tt class="function">find()</tt>. |
| 102 | If no such file is found, then <code>None</code> is returned. If <var>all</var> |
| 103 | is given, it returns a list of all file names, in the order in which |
| 104 | they appear in the languages list or the environment variables. |
| 105 | </dl> |
| 106 | |
| 107 | <P> |
| 108 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 109 | <td><nobr><b><tt id='l2h-2428' xml:id='l2h-2428' class="function">translation</tt></b>(</nobr></td> |
| 110 | <td><var>domain</var><big>[</big><var>, localedir</var><big>[</big><var>, |
| 111 | languages</var><big>[</big><var>, class_</var><big>[</big><var>, |
| 112 | fallback</var><big>[</big><var>, codeset</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 113 | <dd> |
| 114 | Return a <tt class="class">Translations</tt> instance based on the <var>domain</var>, |
| 115 | <var>localedir</var>, and <var>languages</var>, which are first passed to |
| 116 | <tt class="function">find()</tt> to get a list of the |
| 117 | associated <span class="file">.mo</span> file paths. Instances with |
| 118 | identical <span class="file">.mo</span> file names are cached. The actual class instantiated |
| 119 | is either <var>class_</var> if provided, otherwise |
| 120 | <tt class="class">GNUTranslations</tt>. The class's constructor must take a single |
| 121 | file object argument. If provided, <var>codeset</var> will change the |
| 122 | charset used to encode translated strings. |
| 123 | |
| 124 | <P> |
| 125 | If multiple files are found, later files are used as fallbacks for |
| 126 | earlier ones. To allow setting the fallback, <tt class="function">copy.copy</tt> |
| 127 | is used to clone each translation object from the cache; the actual |
| 128 | instance data is still shared with the cache. |
| 129 | |
| 130 | <P> |
| 131 | If no <span class="file">.mo</span> file is found, this function raises |
| 132 | <tt class="exception">IOError</tt> if <var>fallback</var> is false (which is the default), |
| 133 | and returns a <tt class="class">NullTranslations</tt> instance if <var>fallback</var> is |
| 134 | true. |
| 135 | |
| 136 | <P> |
| 137 | |
| 138 | <span class="versionnote">Changed in version 2.4: |
| 139 | Added the <var>codeset</var> parameter.</span> |
| 140 | |
| 141 | </dl> |
| 142 | |
| 143 | <P> |
| 144 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 145 | <td><nobr><b><tt id='l2h-2429' xml:id='l2h-2429' class="function">install</tt></b>(</nobr></td> |
| 146 | <td><var>domain</var><big>[</big><var>, localedir</var><big>[</big><var>, unicode |
| 147 | </var><big>[</big><var>, codeset</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 148 | <dd> |
| 149 | This installs the function <tt class="function">_</tt> in Python's builtin namespace, |
| 150 | based on <var>domain</var>, <var>localedir</var>, and <var>codeset</var> which are |
| 151 | passed to the function <tt class="function">translation()</tt>. The <var>unicode</var> |
| 152 | flag is passed to the resulting translation object's <tt class="method">install</tt> |
| 153 | method. |
| 154 | |
| 155 | <P> |
| 156 | As seen below, you usually mark the strings in your application that are |
| 157 | candidates for translation, by wrapping them in a call to the |
| 158 | <tt class="function">_()</tt> function, like this: |
| 159 | |
| 160 | <P> |
| 161 | <div class="verbatim"><pre> |
| 162 | print _('This string will be translated.') |
| 163 | </pre></div> |
| 164 | |
| 165 | <P> |
| 166 | For convenience, you want the <tt class="function">_()</tt> function to be installed in |
| 167 | Python's builtin namespace, so it is easily accessible in all modules |
| 168 | of your application. |
| 169 | |
| 170 | <P> |
| 171 | |
| 172 | <span class="versionnote">Changed in version 2.4: |
| 173 | Added the <var>codeset</var> parameter.</span> |
| 174 | |
| 175 | </dl> |
| 176 | |
| 177 | <P> |
| 178 | <BR><HR><H4>Footnotes</H4> |
| 179 | <DL> |
| 180 | <DT><A NAME="foot36704">... used.</A><A |
| 181 | HREF="node328.html#tex2html43"><SUP>6.3</SUP></A></DT> |
| 182 | <DD>See the footnote for |
| 183 | <tt class="function">bindtextdomain()</tt> above. |
| 184 | |
| 185 | </DD> |
| 186 | </DL> |
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| 189 | <!--Table of Child-Links--> |
| 190 | <A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a> |
| 191 | |
| 192 | <UL CLASS="ChildLinks"> |
| 193 | <LI><A href="node329.html">6.28.2.1 The <tt class="class">NullTranslations</tt> class</a> |
| 194 | <LI><A href="node330.html">6.28.2.2 The <tt class="class">GNUTranslations</tt> class</a> |
| 195 | <LI><A href="node331.html">6.28.2.3 Solaris message catalog support</a> |
| 196 | <LI><A href="node332.html">6.28.2.4 The Catalog constructor</a> |
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