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Re: [Tutor] working with strings in python3

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On Tue, 2011-04-19 at 02:16 +0000, Steven D'Aprano wrote:
> On Tue, 19 Apr 2011 10:34:27 +1000, James Mills wrote:
> 
> > Normally it's considered bad practise to concatenate strings. 
> 
> *Repeatedly*.
> 
> There's nothing wrong with concatenating (say) two or three strings. 
> What's a bad idea is something like:
> 
> 
> s = ''
> while condition:
>     s += "append stuff to end"
> 
> Even worse:
> 
> s = ''
> while condition:
>     s = "insert stuff at beginning" + s
> 
> because that defeats the runtime optimization (CPython only!) that 
> *sometimes* can alleviate the badness of repeated string concatenation.
> 
> See Joel on Software for more:
> 
> http://www.joelonsoftware.com/articles/fog0000000319.html
> 
> But a single concatenation is more or less equally efficient as string 
> formatting operations (and probably more efficient, because you don't 
> have the overheard of parsing the format mini-language).
> 
> For repeated concatenation, the usual idiom is to collect all the 
> substrings in a list, then join them all at once at the end:
> 
> pieces = []
> while condition:
>     pieces.append('append stuff at end')
> s = ''.join(pieces)
> 
> 
> 
> 
> -- 
> Steven

Thanks Steven, I was about to ask for an efficient way to concatenate an
arbitrary amount of strings.

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Re: [Tutor] working with strings in python3 James Mills <prologic@shortcircuit.net.au> - 2011-04-19 10:34 +1000
  Re: [Tutor] working with strings in python3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-19 02:16 +0000
    Re: [Tutor] working with strings in python3 Chris Angelico <rosuav@gmail.com> - 2011-04-19 13:22 +1000
    Re: [Tutor] working with strings in python3 Westley Martínez <anikom15@gmail.com> - 2011-04-18 20:26 -0700

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