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From: Cameron Simpson <cs@zip.com.au>
Newsgroups: comp.lang.python
Subject: Re: repeat items in a list
Date: Sun, 27 Mar 2016 10:05:47 +1100
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On 26Mar2016 15:12, beliavsky@aol.com <beliavsky@aol.com> wrote:
>I can create a list that has repeated elements of another list as follows:
>
>xx = ["a","b"]
>nrep = 3
>print xx
>yy = []
>for aa in xx:
>    for i in range(nrep):
>        yy.append(aa)
>print yy
>
>output:
>['a', 'b']
>['a', 'a', 'a', 'b', 'b', 'b']
>
>Is there a one-liner to create a list with repeated elements?

Sure. As with all one liners, there comes a degree of complexity when it gets 
in the way of readability; you must decide what is better in your use case.

Look up the chain() function from the itertools module. Generate 2 (or nrep) 
length lists from each element of the original list and chain() them together.  
That gets you an iterable of all the elements. If you really need a list out 
the end instead of the iterable of the elements, convert the iterable to a list 
(hint: lists can be initialised with iterables).

Cheers,
Cameron Simpson <cs@zip.com.au>