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| 16 | <title>7.13.1 Hash, BTree and Record Objects </title> | |
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| 54 | <H2><A NAME="SECTION0091310000000000000000"></A><A NAME="bsddb-objects"></A> | |
| 55 | <BR> | |
| 56 | 7.13.1 Hash, BTree and Record Objects | |
| 57 | </H2> | |
| 58 | ||
| 59 | <P> | |
| 60 | Once instantiated, hash, btree and record objects support | |
| 61 | the same methods as dictionaries. In addition, they support | |
| 62 | the methods listed below. | |
| 63 | ||
| 64 | <span class="versionnote">Changed in version 2.3.1: | |
| 65 | Added dictionary methods.</span> | |
| 66 | ||
| 67 | <P> | |
| 68 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 69 | <td><nobr><b><tt id='l2h-2800' xml:id='l2h-2800' class="method">close</tt></b>(</nobr></td> | |
| 70 | <td><var></var>)</td></tr></table></dt> | |
| 71 | <dd> | |
| 72 | Close the underlying file. The object can no longer be accessed. Since | |
| 73 | there is no open <tt class="method">open</tt> method for these objects, to open the file | |
| 74 | again a new <tt class="module">bsddb</tt> module open function must be called. | |
| 75 | </dl> | |
| 76 | ||
| 77 | <P> | |
| 78 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 79 | <td><nobr><b><tt id='l2h-2801' xml:id='l2h-2801' class="method">keys</tt></b>(</nobr></td> | |
| 80 | <td><var></var>)</td></tr></table></dt> | |
| 81 | <dd> | |
| 82 | Return the list of keys contained in the DB file. The order of the list is | |
| 83 | unspecified and should not be relied on. In particular, the order of the | |
| 84 | list returned is different for different file formats. | |
| 85 | </dl> | |
| 86 | ||
| 87 | <P> | |
| 88 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 89 | <td><nobr><b><tt id='l2h-2802' xml:id='l2h-2802' class="method">has_key</tt></b>(</nobr></td> | |
| 90 | <td><var>key</var>)</td></tr></table></dt> | |
| 91 | <dd> | |
| 92 | Return <code>1</code> if the DB file contains the argument as a key. | |
| 93 | </dl> | |
| 94 | ||
| 95 | <P> | |
| 96 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 97 | <td><nobr><b><tt id='l2h-2803' xml:id='l2h-2803' class="method">set_location</tt></b>(</nobr></td> | |
| 98 | <td><var>key</var>)</td></tr></table></dt> | |
| 99 | <dd> | |
| 100 | Set the cursor to the item indicated by <var>key</var> and return a tuple | |
| 101 | containing the key and its value. For binary tree databases (opened | |
| 102 | using <tt class="function">btopen()</tt>), if <var>key</var> does not actually exist in | |
| 103 | the database, the cursor will point to the next item in sorted order | |
| 104 | and return that key and value. For other databases, | |
| 105 | <tt class="exception">KeyError</tt> will be raised if <var>key</var> is not found in the | |
| 106 | database. | |
| 107 | </dl> | |
| 108 | ||
| 109 | <P> | |
| 110 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 111 | <td><nobr><b><tt id='l2h-2804' xml:id='l2h-2804' class="method">first</tt></b>(</nobr></td> | |
| 112 | <td><var></var>)</td></tr></table></dt> | |
| 113 | <dd> | |
| 114 | Set the cursor to the first item in the DB file and return it. The order of | |
| 115 | keys in the file is unspecified, except in the case of B-Tree databases. | |
| 116 | This method raises <tt class="exception">bsddb.error</tt> if the database is empty. | |
| 117 | </dl> | |
| 118 | ||
| 119 | <P> | |
| 120 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 121 | <td><nobr><b><tt id='l2h-2805' xml:id='l2h-2805' class="method">next</tt></b>(</nobr></td> | |
| 122 | <td><var></var>)</td></tr></table></dt> | |
| 123 | <dd> | |
| 124 | Set the cursor to the next item in the DB file and return it. The order of | |
| 125 | keys in the file is unspecified, except in the case of B-Tree databases. | |
| 126 | </dl> | |
| 127 | ||
| 128 | <P> | |
| 129 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 130 | <td><nobr><b><tt id='l2h-2806' xml:id='l2h-2806' class="method">previous</tt></b>(</nobr></td> | |
| 131 | <td><var></var>)</td></tr></table></dt> | |
| 132 | <dd> | |
| 133 | Set the cursor to the previous item in the DB file and return it. The | |
| 134 | order of keys in the file is unspecified, except in the case of B-Tree | |
| 135 | databases. This is not supported on hashtable databases (those opened | |
| 136 | with <tt class="function">hashopen()</tt>). | |
| 137 | </dl> | |
| 138 | ||
| 139 | <P> | |
| 140 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 141 | <td><nobr><b><tt id='l2h-2807' xml:id='l2h-2807' class="method">last</tt></b>(</nobr></td> | |
| 142 | <td><var></var>)</td></tr></table></dt> | |
| 143 | <dd> | |
| 144 | Set the cursor to the last item in the DB file and return it. The | |
| 145 | order of keys in the file is unspecified. This is not supported on | |
| 146 | hashtable databases (those opened with <tt class="function">hashopen()</tt>). | |
| 147 | This method raises <tt class="exception">bsddb.error</tt> if the database is empty. | |
| 148 | </dl> | |
| 149 | ||
| 150 | <P> | |
| 151 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 152 | <td><nobr><b><tt id='l2h-2808' xml:id='l2h-2808' class="method">sync</tt></b>(</nobr></td> | |
| 153 | <td><var></var>)</td></tr></table></dt> | |
| 154 | <dd> | |
| 155 | Synchronize the database on disk. | |
| 156 | </dl> | |
| 157 | ||
| 158 | <P> | |
| 159 | Example: | |
| 160 | ||
| 161 | <P> | |
| 162 | <div class="verbatim"><pre> | |
| 163 | >>> import bsddb | |
| 164 | >>> db = bsddb.btopen('/tmp/spam.db', 'c') | |
| 165 | >>> for i in range(10): db['%d'%i] = '%d'% (i*i) | |
| 166 | ... | |
| 167 | >>> db['3'] | |
| 168 | '9' | |
| 169 | >>> db.keys() | |
| 170 | ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'] | |
| 171 | >>> db.first() | |
| 172 | ('0', '0') | |
| 173 | >>> db.next() | |
| 174 | ('1', '1') | |
| 175 | >>> db.last() | |
| 176 | ('9', '81') | |
| 177 | >>> db.set_location('2') | |
| 178 | ('2', '4') | |
| 179 | >>> db.previous() | |
| 180 | ('1', '1') | |
| 181 | >>> for k, v in db.iteritems(): | |
| 182 | ... print k, v | |
| 183 | 0 0 | |
| 184 | 1 1 | |
| 185 | 2 4 | |
| 186 | 3 9 | |
| 187 | 4 16 | |
| 188 | 5 25 | |
| 189 | 6 36 | |
| 190 | 7 49 | |
| 191 | 8 64 | |
| 192 | 9 81 | |
| 193 | >>> '8' in db | |
| 194 | True | |
| 195 | >>> db.sync() | |
| 196 | 0 | |
| 197 | </pre></div> | |
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| 233 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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