title: Understanding DictVectorizer in scikit-learn?
body: <p>I'm exploring the different feature extraction classes that <code>scikit-learn</code> provides. Reading the <a href="http://scikit-learn.org/stable/modules/generated/sklearn.feature_extraction.DictVectorizer.html" rel="noreferrer">documentation</a> I did not understand very well what <code>DictVectorizer</code> can be used for? Other questions come to mind. For example, how can <code>DictVectorizer</code> be used for text classification?, i.e. how does this class help handle labelled textual data? Could anybody provide a short example apart from the <a href="http://scikit-learn.org/stable/modules/generated/sklearn.feature_extraction.DictVectorizer.html" rel="noreferrer">example</a> that I already read at the documentation web page?</p>