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mention using the in operator on a dictionary

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Mark Pilgrim
2009-06-26 01:11:57 -04:00
parent 46a634031c
commit c74db78967
1 changed files with 8 additions and 5 deletions
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@@ -505,15 +505,18 @@ KeyError: 'db.diveintopython3.org'</samp></pre>
<samp class=p>... </samp><kbd class=pp> 1024: ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']}</kbd>
<a><samp class=p>>>> </samp><kbd class=pp>len(SUFFIXES)</kbd> <span class=u>&#x2460;</span></a>
<samp class=pp>2</samp>
<a><samp class=p>>>> </samp><kbd class=pp>SUFFIXES[1000]</kbd> <span class=u>&#x2461;</span></a>
<a><samp class=p>>>> </samp><kbd class=pp>1000 in SUFFIXES</kbd> <span class=u>&#x2461;</span></a>
<samp class=pp>True</samp>
<a><samp class=p>>>> </samp><kbd class=pp>SUFFIXES[1000]</kbd> <span class=u>&#x2462;</span></a>
<samp class=pp>['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']</samp>
<a><samp class=p>>>> </samp><kbd class=pp>SUFFIXES[1024]</kbd> <span class=u>&#x2462;</span></a>
<a><samp class=p>>>> </samp><kbd class=pp>SUFFIXES[1024]</kbd> <span class=u>&#x2463;</span></a>
<samp class=pp>['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']</samp>
<a><samp class=p>>>> </samp><kbd class=pp>SUFFIXES[1000][3]</kbd> <span class=u>&#x2463;</span></a>
<a><samp class=p>>>> </samp><kbd class=pp>SUFFIXES[1000][3]</kbd> <span class=u>&#x2464;</span></a>
<samp class=pp>'TB'</samp></pre>
<ol>
<li>As with <a href=#lists>lists</a><!-- and <a href=#sets>sets</a>-->, the <code>len()</code> function gives you the number of items in a dictionary.
<li><code>1000</code> is a key in the <code>SUFFIXES</code> dictionary; its value is a list of eight items (eight strings, to be precise).
<li>Like <a href=#lists>lists</a> and <a href=#sets>sets</a> [FIXME-xref], the <code>len()</code> function gives you the number of keys in a dictionary.
<li>And like lists and sets, you can use the <code>in</code> operator to test whether a specific key is defined in a dictionary.
<li><code>1000</code> <em>is</em> a key in the <code>SUFFIXES</code> dictionary; its value is a list of eight items (eight strings, to be precise).
<li>Similarly, <code>1024</code> is a key in the <code>SUFFIXES</code> dictionary; its value is also a list of eight items.
<li>Since <code>SUFFIXES[1000]</code> is a list, you can address individual items in the list by their 0-based index.
</ol>