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| 55 | <H3><A NAME="SECTION0082822000000000000000"> |
| 56 | 6.28.2.2 The <tt class="class">GNUTranslations</tt> class</A> |
| 57 | </H3> |
| 58 | |
| 59 | <P> |
| 60 | The <tt class="module">gettext</tt> module provides one additional class derived from |
| 61 | <tt class="class">NullTranslations</tt>: <tt class="class">GNUTranslations</tt>. This class |
| 62 | overrides <tt class="method">_parse()</tt> to enable reading GNU <b class="program">gettext</b> |
| 63 | format <span class="file">.mo</span> files in both big-endian and little-endian format. |
| 64 | It also coerces both message ids and message strings to Unicode. |
| 65 | |
| 66 | <P> |
| 67 | <tt class="class">GNUTranslations</tt> parses optional meta-data out of the |
| 68 | translation catalog. It is convention with GNU <b class="program">gettext</b> to |
| 69 | include meta-data as the translation for the empty string. This |
| 70 | meta-data is in <a class="rfc" id='rfcref-88910' xml:id='rfcref-88910' |
| 71 | href="http://www.faqs.org/rfcs/rfc822.html">RFC 822</a>-style <code>key: value</code> pairs, and should |
| 72 | contain the <code>Project-Id-Version</code> key. If the key |
| 73 | <code>Content-Type</code> is found, then the <code>charset</code> property is used |
| 74 | to initialize the ``protected'' <tt class="member">_charset</tt> instance variable, |
| 75 | defaulting to <code>None</code> if not found. If the charset encoding is |
| 76 | specified, then all message ids and message strings read from the |
| 77 | catalog are converted to Unicode using this encoding. The |
| 78 | <tt class="method">ugettext()</tt> method always returns a Unicode, while the |
| 79 | <tt class="method">gettext()</tt> returns an encoded 8-bit string. For the message |
| 80 | id arguments of both methods, either Unicode strings or 8-bit strings |
| 81 | containing only US-ASCII characters are acceptable. Note that the |
| 82 | Unicode version of the methods (i.e. <tt class="method">ugettext()</tt> and |
| 83 | <tt class="method">ungettext()</tt>) are the recommended interface to use for |
| 84 | internationalized Python programs. |
| 85 | |
| 86 | <P> |
| 87 | The entire set of key/value pairs are placed into a dictionary and set |
| 88 | as the ``protected'' <tt class="member">_info</tt> instance variable. |
| 89 | |
| 90 | <P> |
| 91 | If the <span class="file">.mo</span> file's magic number is invalid, or if other problems |
| 92 | occur while reading the file, instantiating a <tt class="class">GNUTranslations</tt> class |
| 93 | can raise <tt class="exception">IOError</tt>. |
| 94 | |
| 95 | <P> |
| 96 | The following methods are overridden from the base class implementation: |
| 97 | |
| 98 | <P> |
| 99 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 100 | <td><nobr><b><tt id='l2h-2448' xml:id='l2h-2448' class="method">gettext</tt></b>(</nobr></td> |
| 101 | <td><var>message</var>)</td></tr></table></dt> |
| 102 | <dd> |
| 103 | Look up the <var>message</var> id in the catalog and return the |
| 104 | corresponding message string, as an 8-bit string encoded with the |
| 105 | catalog's charset encoding, if known. If there is no entry in the |
| 106 | catalog for the <var>message</var> id, and a fallback has been set, the |
| 107 | look up is forwarded to the fallback's <tt class="method">gettext()</tt> method. |
| 108 | Otherwise, the <var>message</var> id is returned. |
| 109 | </dl> |
| 110 | |
| 111 | <P> |
| 112 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 113 | <td><nobr><b><tt id='l2h-2449' xml:id='l2h-2449' class="method">lgettext</tt></b>(</nobr></td> |
| 114 | <td><var>message</var>)</td></tr></table></dt> |
| 115 | <dd> |
| 116 | Equivalent to <tt class="method">gettext()</tt>, but the translation is returned |
| 117 | in the preferred system encoding, if no other encoding was explicitly |
| 118 | set with <tt class="method">set_output_charset()</tt>. |
| 119 | |
| 120 | <P> |
| 121 | |
| 122 | <span class="versionnote">New in version 2.4.</span> |
| 123 | |
| 124 | </dl> |
| 125 | |
| 126 | <P> |
| 127 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 128 | <td><nobr><b><tt id='l2h-2450' xml:id='l2h-2450' class="method">ugettext</tt></b>(</nobr></td> |
| 129 | <td><var>message</var>)</td></tr></table></dt> |
| 130 | <dd> |
| 131 | Look up the <var>message</var> id in the catalog and return the |
| 132 | corresponding message string, as a Unicode string. If there is no |
| 133 | entry in the catalog for the <var>message</var> id, and a fallback has been |
| 134 | set, the look up is forwarded to the fallback's <tt class="method">ugettext()</tt> |
| 135 | method. Otherwise, the <var>message</var> id is returned. |
| 136 | </dl> |
| 137 | |
| 138 | <P> |
| 139 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 140 | <td><nobr><b><tt id='l2h-2451' xml:id='l2h-2451' class="method">ngettext</tt></b>(</nobr></td> |
| 141 | <td><var>singular, plural, n</var>)</td></tr></table></dt> |
| 142 | <dd> |
| 143 | Do a plural-forms lookup of a message id. <var>singular</var> is used as |
| 144 | the message id for purposes of lookup in the catalog, while <var>n</var> is |
| 145 | used to determine which plural form to use. The returned message |
| 146 | string is an 8-bit string encoded with the catalog's charset encoding, |
| 147 | if known. |
| 148 | |
| 149 | <P> |
| 150 | If the message id is not found in the catalog, and a fallback is |
| 151 | specified, the request is forwarded to the fallback's |
| 152 | <tt class="method">ngettext()</tt> method. Otherwise, when <var>n</var> is 1 <var>singular</var> is |
| 153 | returned, and <var>plural</var> is returned in all other cases. |
| 154 | |
| 155 | <P> |
| 156 | |
| 157 | <span class="versionnote">New in version 2.3.</span> |
| 158 | |
| 159 | </dl> |
| 160 | |
| 161 | <P> |
| 162 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 163 | <td><nobr><b><tt id='l2h-2452' xml:id='l2h-2452' class="method">lngettext</tt></b>(</nobr></td> |
| 164 | <td><var>singular, plural, n</var>)</td></tr></table></dt> |
| 165 | <dd> |
| 166 | Equivalent to <tt class="method">gettext()</tt>, but the translation is returned |
| 167 | in the preferred system encoding, if no other encoding was explicitly |
| 168 | set with <tt class="method">set_output_charset()</tt>. |
| 169 | |
| 170 | <P> |
| 171 | |
| 172 | <span class="versionnote">New in version 2.4.</span> |
| 173 | |
| 174 | </dl> |
| 175 | |
| 176 | <P> |
| 177 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 178 | <td><nobr><b><tt id='l2h-2453' xml:id='l2h-2453' class="method">ungettext</tt></b>(</nobr></td> |
| 179 | <td><var>singular, plural, n</var>)</td></tr></table></dt> |
| 180 | <dd> |
| 181 | Do a plural-forms lookup of a message id. <var>singular</var> is used as |
| 182 | the message id for purposes of lookup in the catalog, while <var>n</var> is |
| 183 | used to determine which plural form to use. The returned message |
| 184 | string is a Unicode string. |
| 185 | |
| 186 | <P> |
| 187 | If the message id is not found in the catalog, and a fallback is |
| 188 | specified, the request is forwarded to the fallback's |
| 189 | <tt class="method">ungettext()</tt> method. Otherwise, when <var>n</var> is 1 <var>singular</var> is |
| 190 | returned, and <var>plural</var> is returned in all other cases. |
| 191 | |
| 192 | <P> |
| 193 | Here is an example: |
| 194 | |
| 195 | <P> |
| 196 | <div class="verbatim"><pre> |
| 197 | n = len(os.listdir('.')) |
| 198 | cat = GNUTranslations(somefile) |
| 199 | message = cat.ungettext( |
| 200 | 'There is %(num)d file in this directory', |
| 201 | 'There are %(num)d files in this directory', |
| 202 | n) % {'num': n} |
| 203 | </pre></div> |
| 204 | |
| 205 | <P> |
| 206 | |
| 207 | <span class="versionnote">New in version 2.3.</span> |
| 208 | |
| 209 | </dl> |
| 210 | |
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