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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: How to iterate on a changing dictionary
Date: Sun, 19 Jun 2011 12:51:06 -0400
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:7982

On 6/19/2011 11:53 AM, Roy Smith wrote:

> Yet another variation which makes sense if you want to delete most of
> the keys would be to copy them to a new dictionary.  I'm not sure how
> Python handles memory management on dictionaries which shrink.

'Python' does not handle memory management; each implementation does -).
I believe CPython will shrink lists and dicts that are too empty, but it 
should be both more efficient and more dependable to make a new one as 
with your code or

old_d = {i:i for i in range(100)}
d = {key:val for key,val in old_d.items() if not key%13}
d
 >>>
{0: 0, 65: 65, 39: 39, 13: 13, 78: 78, 52: 52, 26: 26, 91: 91}

-- 
Terry Jan Reedy