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<p>如何通过词典理解对词典进行迭代处理。</p>
<pre><code>>>> mime_types={
'.xbm': 'image/x-xbitmap',
'.dwg': 'image/vnd.dwg',
'.fst': 'image/vnd.fst',
'.tif': 'image/tiff',
'.gif': 'image/gif',
'.ras': 'image/x-cmu-raster',
'.pic': 'image/x-pict',
'.fh': 'image/x-freehand',
'.djvu':'image/vnd.djvu',
'.ppm': 'image/x-portable-pixmap',
'.fh4': 'image/x-freehand',
'.cgm': 'image/cgm',
'.xwd': 'image/x-xwindowdump',
'.g3': 'image/g3fax',
'.png': 'image/png',
'.npx': 'image/vnd.net-fpx',
'.rlc': 'image/vnd.fujixerox.edmics-rlc',
'.svgz':'image/svg+xml',
'.mmr': 'image/vnd.fujixerox.edmics-mmr',
'.psd': 'image/vnd.adobe.photoshop',
'.oti': 'application/vnd.oasis.opendocument.image-template',
'.tiff':'image/tiff',
'.wbmp':'image/vnd.wap.wbmp'
}
>>> {(key,val) for key, val in mime_types.items() if "image/tiff" == val}
</code></pre>
<p>这将返回如下结果:</p>
<pre><code>set([('.tiff', 'image/tiff'), ('.tif', 'image/tiff')])
</code></pre>
<p>但我期待着</p>
<pre><code>('.tif', 'image/tiff')
</code></pre>
<p>如何修改该结果以获得如下词典:</p>
<pre><code>{'.tif': 'image/tiff'}
</code></pre>