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From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.python
Subject: Re: repeat items in a list
Date: Sat, 26 Mar 2016 22:35:28 -0700
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beliavsky@aol.com writes:
> yy = list(chain.from_iterable([list(repeat(aa,nrep)) for aa in xx]))

The chain approach seems more natural to me:

  yy = list(chain.from_iterable(map(lambda x: [x,x], xx)))

may make the doubling more obvious, and in Python 3 it should avoid the
intermediate lists since map creates a generator.  Depending on the
usage, you might also not need the outermost list, making yy a lazy
generator as well.