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Re: Find and Replace Simplification

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On 20 July 2013 12:57, Serhiy Storchaka <storchaka@gmail.com> wrote:
> 20.07.13 14:16, Joshua Landau написав(ла):
>>
>> On 19 July 2013 18:29, Serhiy Storchaka <storchaka@gmail.com> wrote:
>>>
>>> The string replace() method is fastest (at least in Python 3.3+). See
>>> implementation of html.escape() etc.
>>
>>
>> def escape(s, quote=True):
>>      if quote:
>>          return s.translate(_escape_map_full)
>>      return s.translate(_escape_map)
>>
>> I fail to see how this supports the assertion that str.replace() is
>> faster.
>
>
> And now look at Python 3.4 sources.

I'll just trust you ;).

>> However, some quick timing shows that translate has a very
>> high penalty for missing characters and is a tad slower any way.
>>
>> Really, though, there should be no reason for .translate() to be
>> slower than replace -- at worst it should just be "reduce(lambda s,
>> ab: s.replace(*ab), mapping.items()¹, original_str)" and end up the
>> *same* speed as iterated replace.
>
>
> It doesn't work such way. Consider
> 'ab'.translate({ord('a'):'b',ord('b'):'a'}).

*sad*

Still, it seems to me that it should be optimizable for sensible
builtin types such that .translate is significantly faster, as there's
no theoretical extra work that .translate *has* to do that .replace
does not, and .replace also has to rebuild the string a lot of times.

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Thread

Find and Replace Simplification Devyn Collier Johnson <devyncjohnson@gmail.com> - 2013-07-19 09:22 -0400
  Re: Find and Replace Simplification Novocastrian_Nomad <gregory.j.baker@gmail.com> - 2013-07-19 06:38 -0700
  Re: Find and Replace Simplification John Gordon <gordon@panix.com> - 2013-07-19 14:28 +0000
  Re: Find and Replace Simplification Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-19 16:22 +0000
    Re: Find and Replace Simplification Serhiy Storchaka <storchaka@gmail.com> - 2013-07-19 20:29 +0300
    Re: Find and Replace Simplification Skip Montanaro <skip@pobox.com> - 2013-07-19 13:08 -0500
    Re: Find and Replace Simplification Devyn Collier Johnson <devyncjohnson@gmail.com> - 2013-07-19 17:44 -0400
    Re: Find and Replace Simplification Dave Angel <davea@davea.name> - 2013-07-19 18:45 -0400
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-20 12:16 +0100
    Re: Find and Replace Simplification Serhiy Storchaka <storchaka@gmail.com> - 2013-07-20 14:48 +0300
    Re: Find and Replace Simplification Serhiy Storchaka <storchaka@gmail.com> - 2013-07-20 14:57 +0300
    Re: Find and Replace Simplification Devyn Collier Johnson <devyncjohnson@gmail.com> - 2013-07-20 08:41 -0400
    Re: Find and Replace Simplification Devyn Collier Johnson <devyncjohnson@gmail.com> - 2013-07-20 08:50 -0400
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-20 18:03 +0100
    Re: Find and Replace Simplification Dave Angel <davea@davea.name> - 2013-07-20 14:04 -0400
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-20 19:37 +0100
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-20 19:41 +0100
    Re: Find and Replace Simplification Dave Angel <davea@davea.name> - 2013-07-20 17:56 -0400
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-20 23:33 +0100
    Re: Find and Replace Simplification Serhiy Storchaka <storchaka@gmail.com> - 2013-07-21 10:44 +0300
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-21 12:29 +0100
    Re: Find and Replace Simplification Serhiy Storchaka <storchaka@gmail.com> - 2013-07-21 15:28 +0300
    Re: Find and Replace Simplification Joshua Landau <joshua@landau.ws> - 2013-07-21 13:49 +0100

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