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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: relative speed of incremention syntaxes (or "i=i+1" VS "i+=1")
Date: Sun, 21 Aug 2011 22:15:07 -0400
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:11987

On 8/21/2011 7:49 PM, Laurent Payot wrote:
> I made Python my language of choice because of its readability and
> simpleness, and not because of its speed. But it's always good to
> know what is the fastest sometimes when you don't want to write a
> module in C. So I was just wondering if there was a difference. There
> is, of a few percent. Anyway I will keep on using the 2% slower "i +=
> 1" because for me that's less prone to errors because you write the
> variable only once, and that's more important than speed.

For longer variable names, it is also easier and faster to read once one 
gets used to the idiom.

number_of_chars += 1 # versus
number_of_chars = number_of_chars + 1

Not repeating was a major reason for the addition.

-- 
Terry Jan Reedy