<p><a href="http://metaoptimize.com/qa/questions/6943/what-is-the-hashing-trick#6945" rel="nofollow">Here</a> (sorry I cannot add this as a comment for some reason.) Also, the first page of <a href="http://arxiv.org/pdf/0902.2206" rel="nofollow">Feature Hashing for Large Scale Multitask Learning</a> explains it nicely.</p>
What is feature hashing (hashing-trick)?
<p>I know feature hashing (hashing-trick) is used to reduce the dimensionality and handle sparsity of bit vectors but I don't understand how it really works. Can anyone explain this to me.Is there any python library available to do feature hashing?</p>

<p>Thank you.</p>