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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: L[:]
Date: Tue, 14 Jan 2014 17:07:15 -0500
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Xref: csiph.com comp.lang.python:63951

On 1/14/2014 5:42 AM, Albert-Jan Roskam wrote:

> I also found that item assignment ([1] below) is much faster
 > than using the more standard (I think) .append ([2]).

> # [1]
> for idx,item in enumerate(L[:]):
>     if some_condition:
>        L[idx] = foobarify(item)

[1] *is* the standard way to selectively replace items.

> # [2]
> L2 = []
> for idx,item in enumerate(L):
>     if some_condition:
>         L2.append(foobarify(item))
>     else:
>         L2.append(item)

-- 
Terry Jan Reedy