| 1 | <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
| 2 | <html> |
| 3 | <head> |
| 4 | <link rel="STYLESHEET" href="lib.css" type='text/css' /> |
| 5 | <link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" /> |
| 6 | <link rel='start' href='../index.html' title='Python Documentation Index' /> |
| 7 | <link rel="first" href="lib.html" title='Python Library Reference' /> |
| 8 | <link rel='contents' href='contents.html' title="Contents" /> |
| 9 | <link rel='index' href='genindex.html' title='Index' /> |
| 10 | <link rel='last' href='about.html' title='About this document...' /> |
| 11 | <link rel='help' href='about.html' title='About this document...' /> |
| 12 | <link rel="prev" href="node76.html" /> |
| 13 | <link rel="parent" href="module-shelve.html" /> |
| 14 | <link rel="next" href="module-copy.html" /> |
| 15 | <meta name='aesop' content='information' /> |
| 16 | <title>3.17.2 Example</title> |
| 17 | </head> |
| 18 | <body> |
| 19 | <DIV CLASS="navigation"> |
| 20 | <div id='top-navigation-panel' xml:id='top-navigation-panel'> |
| 21 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> |
| 22 | <tr> |
| 23 | <td class='online-navigation'><a rel="prev" title="3.17.1 Restrictions" |
| 24 | href="node76.html"><img src='../icons/previous.png' |
| 25 | border='0' height='32' alt='Previous Page' width='32' /></A></td> |
| 26 | <td class='online-navigation'><a rel="parent" title="3.17 shelve " |
| 27 | href="module-shelve.html"><img src='../icons/up.png' |
| 28 | border='0' height='32' alt='Up One Level' width='32' /></A></td> |
| 29 | <td class='online-navigation'><a rel="next" title="3.18 copy " |
| 30 | href="module-copy.html"><img src='../icons/next.png' |
| 31 | border='0' height='32' alt='Next Page' width='32' /></A></td> |
| 32 | <td align="center" width="100%">Python Library Reference</td> |
| 33 | <td class='online-navigation'><a rel="contents" title="Table of Contents" |
| 34 | href="contents.html"><img src='../icons/contents.png' |
| 35 | border='0' height='32' alt='Contents' width='32' /></A></td> |
| 36 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' |
| 37 | border='0' height='32' alt='Module Index' width='32' /></a></td> |
| 38 | <td class='online-navigation'><a rel="index" title="Index" |
| 39 | href="genindex.html"><img src='../icons/index.png' |
| 40 | border='0' height='32' alt='Index' width='32' /></A></td> |
| 41 | </tr></table> |
| 42 | <div class='online-navigation'> |
| 43 | <b class="navlabel">Previous:</b> |
| 44 | <a class="sectref" rel="prev" href="node76.html">3.17.1 Restrictions</A> |
| 45 | <b class="navlabel">Up:</b> |
| 46 | <a class="sectref" rel="parent" href="module-shelve.html">3.17 shelve </A> |
| 47 | <b class="navlabel">Next:</b> |
| 48 | <a class="sectref" rel="next" href="module-copy.html">3.18 copy </A> |
| 49 | </div> |
| 50 | <hr /></div> |
| 51 | </DIV> |
| 52 | <!--End of Navigation Panel--> |
| 53 | |
| 54 | <H2><A NAME="SECTION0051720000000000000000"> |
| 55 | 3.17.2 Example</A> |
| 56 | </H2> |
| 57 | |
| 58 | <P> |
| 59 | To summarize the interface (<code>key</code> is a string, <code>data</code> is an |
| 60 | arbitrary object): |
| 61 | |
| 62 | <P> |
| 63 | <div class="verbatim"><pre> |
| 64 | import shelve |
| 65 | |
| 66 | d = shelve.open(filename) # open -- file may get suffix added by low-level |
| 67 | # library |
| 68 | |
| 69 | d[key] = data # store data at key (overwrites old data if |
| 70 | # using an existing key) |
| 71 | data = d[key] # retrieve a COPY of data at key (raise KeyError if no |
| 72 | # such key) |
| 73 | del d[key] # delete data stored at key (raises KeyError |
| 74 | # if no such key) |
| 75 | flag = d.has_key(key) # true if the key exists |
| 76 | list = d.keys() # a list of all existing keys (slow!) |
| 77 | |
| 78 | # as d was opened WITHOUT writeback=True, beware: |
| 79 | d['xx'] = range(4) # this works as expected, but... |
| 80 | d['xx'].append(5) # *this doesn't!* -- d['xx'] is STILL range(4)!!! |
| 81 | # having opened d without writeback=True, you need to code carefully: |
| 82 | temp = d['xx'] # extracts the copy |
| 83 | temp.append(5) # mutates the copy |
| 84 | d['xx'] = temp # stores the copy right back, to persist it |
| 85 | # or, d=shelve.open(filename,writeback=True) would let you just code |
| 86 | # d['xx'].append(5) and have it work as expected, BUT it would also |
| 87 | # consume more memory and make the d.close() operation slower. |
| 88 | |
| 89 | d.close() # close it |
| 90 | </pre></div> |
| 91 | |
| 92 | <P> |
| 93 | <div class="seealso"> |
| 94 | <p class="heading">See Also:</p> |
| 95 | |
| 96 | <dl compact="compact" class="seemodule"> |
| 97 | <dt>Module <b><tt class="module"><a href="module-anydbm.html">anydbm</a></tt>:</b> |
| 98 | <dd>Generic interface to <code>dbm</code>-style databases. |
| 99 | </dl> |
| 100 | <dl compact="compact" class="seemodule"> |
| 101 | <dt>Module <b><tt class="module"><a href="module-bsddb.html">bsddb</a></tt>:</b> |
| 102 | <dd>BSD <code>db</code> database interface. |
| 103 | </dl> |
| 104 | <dl compact="compact" class="seemodule"> |
| 105 | <dt>Module <b><tt class="module"><a href="module-dbhash.html">dbhash</a></tt>:</b> |
| 106 | <dd>Thin layer around the <tt class="module">bsddb</tt> which provides an |
| 107 | <tt class="function">open</tt> function like the other database modules. |
| 108 | </dl> |
| 109 | <dl compact="compact" class="seemodule"> |
| 110 | <dt>Module <b><tt class="module"><a href="module-dbm.html">dbm</a></tt>:</b> |
| 111 | <dd>Standard <span class="Unix">Unix</span> database interface. |
| 112 | </dl> |
| 113 | <dl compact="compact" class="seemodule"> |
| 114 | <dt>Module <b><tt class="module"><a href="module-dumbdbm.html">dumbdbm</a></tt>:</b> |
| 115 | <dd>Portable implementation of the <code>dbm</code> interface. |
| 116 | </dl> |
| 117 | <dl compact="compact" class="seemodule"> |
| 118 | <dt>Module <b><tt class="module"><a href="module-gdbm.html">gdbm</a></tt>:</b> |
| 119 | <dd>GNU database interface, based on the <code>dbm</code> interface. |
| 120 | </dl> |
| 121 | <dl compact="compact" class="seemodule"> |
| 122 | <dt>Module <b><tt class="module"><a href="module-pickle.html">pickle</a></tt>:</b> |
| 123 | <dd>Object serialization used by <tt class="module">shelve</tt>. |
| 124 | </dl> |
| 125 | <dl compact="compact" class="seemodule"> |
| 126 | <dt>Module <b><tt class="module"><a href="module-cPickle.html">cPickle</a></tt>:</b> |
| 127 | <dd>High-performance version of <tt class="module"><a href="module-pickle.html">pickle</a></tt>. |
| 128 | </dl> |
| 129 | </div> |
| 130 | |
| 131 | <DIV CLASS="navigation"> |
| 132 | <div class='online-navigation'> |
| 133 | <p></p><hr /> |
| 134 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> |
| 135 | <tr> |
| 136 | <td class='online-navigation'><a rel="prev" title="3.17.1 Restrictions" |
| 137 | href="node76.html"><img src='../icons/previous.png' |
| 138 | border='0' height='32' alt='Previous Page' width='32' /></A></td> |
| 139 | <td class='online-navigation'><a rel="parent" title="3.17 shelve " |
| 140 | href="module-shelve.html"><img src='../icons/up.png' |
| 141 | border='0' height='32' alt='Up One Level' width='32' /></A></td> |
| 142 | <td class='online-navigation'><a rel="next" title="3.18 copy " |
| 143 | href="module-copy.html"><img src='../icons/next.png' |
| 144 | border='0' height='32' alt='Next Page' width='32' /></A></td> |
| 145 | <td align="center" width="100%">Python Library Reference</td> |
| 146 | <td class='online-navigation'><a rel="contents" title="Table of Contents" |
| 147 | href="contents.html"><img src='../icons/contents.png' |
| 148 | border='0' height='32' alt='Contents' width='32' /></A></td> |
| 149 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' |
| 150 | border='0' height='32' alt='Module Index' width='32' /></a></td> |
| 151 | <td class='online-navigation'><a rel="index" title="Index" |
| 152 | href="genindex.html"><img src='../icons/index.png' |
| 153 | border='0' height='32' alt='Index' width='32' /></A></td> |
| 154 | </tr></table> |
| 155 | <div class='online-navigation'> |
| 156 | <b class="navlabel">Previous:</b> |
| 157 | <a class="sectref" rel="prev" href="node76.html">3.17.1 Restrictions</A> |
| 158 | <b class="navlabel">Up:</b> |
| 159 | <a class="sectref" rel="parent" href="module-shelve.html">3.17 shelve </A> |
| 160 | <b class="navlabel">Next:</b> |
| 161 | <a class="sectref" rel="next" href="module-copy.html">3.18 copy </A> |
| 162 | </div> |
| 163 | </div> |
| 164 | <hr /> |
| 165 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
| 166 | </DIV> |
| 167 | <!--End of Navigation Panel--> |
| 168 | <ADDRESS> |
| 169 | See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. |
| 170 | </ADDRESS> |
| 171 | </BODY> |
| 172 | </HTML> |