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From: Serhiy Storchaka <storchaka@gmail.com>
Subject: Re: Find and Replace Simplification
Date: Sat, 20 Jul 2013 14:57:02 +0300
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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.

> 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'}).