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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Thu, 7 Feb 2013 17:55:31 -0700
Subject: Re: Curious to see alternate approach on a search/replace via regex
To: Python <python-list@python.org>
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On Thu, Feb 7, 2013 at 4:59 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> Oh, one last thing... pulling out "re.compile" outside of the function does
> absolutely nothing. You don't even compile anything. It basically looks up
> that a compile function exists in the re module, and that's all.

Using Python 2.7:

>>> t1 = Timer("""
... nx = re.compile(r'https?://(.+)$')
... v = nx.search(u).group(1)
... ux = re.compile(r'([-:./?&=]+)')
... ux.sub('_', v)""", """
... import re
... u = 'http://alongnameofasite1234567.com/q?sports=run&a=1&b=1'""")
>>> t2 = Timer("""
... v = nx.search(u).group(1)
... ux.sub('_', v)""", """
... import re
... nx = re.compile(r'https?://(.+)$')
... ux = re.compile(r'([-:./?&=]+)')
... u = 'http://alongnameofasite1234567.com/q?sports=run&a=1&b=1'""")
>>> min(t1.repeat())
11.625409933385388
>>> min(t2.repeat())
8.825254885746652

Whatever caching is being done by re.compile, that's still a 24%
savings by moving the compile calls into the setup.