projects / OpenSPARC-T2-SAM / blame
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| 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>. | |
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| 165 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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