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List:       python-dev
Subject:    [Python-Dev] Rehashing in PyDict_Copy
From:       guido () python ! org (Guido van Rossum)
Date:       2002-08-29 19:30:52
Message-ID: 200208291930.g7TJUqf02625 () odiug ! zope ! com
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> Is there a reason that dict.copy() runs like an update()?
> It creates a new dict object, then re-hashes and inserts
> every element one-by-one, complete with collisions.
> 
> I would have expected a single pass to update refcounts,
> an allocation for identical size, and a memcpy to polish
> it off.

After you've inserted and removed many elements into a dict, the
elements may not be in the best order, and there may be many "deleted"
markers.  The update() strategy avoids copying such cruft.

--Guido van Rossum (home page: http://www.python.org/~guido/)



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