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Re: re.search when used within an if/else fails

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On Tue, Nov 20, 2012 at 12:37 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Tue, Nov 20, 2012 at 12:09 PM, Kevin T <kevinintx@gmail.com> wrote:
>> #if re.search( "rsrvd", sigName ) :   #version a
>> #if re.search( "rsrvd", sigName ) == None :   #version b
>> if re.search( "rsrvd", sigName ) is None :   #version bb
>>    print sigName
>>    newVal = "%s%s" % ('1'*signal['bits'] , newVal )
>> #else:                                 #version c
>> if re.search( "rsrvd", sigName ) != None :   #version d
>>    print sigName
>>    newVal = "%s%s" % ( '0'*signal['bits'],> newVal )
>>
>> i can use either version a/b the else clause (version c) will not execute.
>> fortunately,  with version bb, the else clause will execute!!
>
> There must be some other difference in your testing.  I don't have
> Python 2.4 available, but I tried your version a in both Python 2.3
> and 2.5 using made-up values for sigName, and the else clause is
> executed in both.

It should be noted, however, that version a is the logical *inverse*
of both b and bb.  With version a, you're testing for the logical
truth of the re.search result; it will be true if it is *not* None.
With the other two you are testing that the result *is* None.

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re.search when used within an if/else fails Kevin T <kevinintx@gmail.com> - 2012-11-19 15:43 -0800
  Re: re.search when used within an if/else fails MRAB <python@mrabarnett.plus.com> - 2012-11-20 01:21 +0000
  Re: re.search when used within an if/else fails Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-20 01:24 +0000
    Re: re.search when used within an if/else fails Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-20 01:29 +0000
      Re: re.search when used within an if/else fails Kevin T <kevinintx@gmail.com> - 2012-11-20 11:09 -0800
        Re: re.search when used within an if/else fails Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-20 12:37 -0700
          Re: re.search when used within an if/else fails Kevin T <kevinintx@gmail.com> - 2012-11-21 08:41 -0800
            Re: re.search when used within an if/else fails Chris Angelico <rosuav@gmail.com> - 2012-11-22 16:00 +1100
              Re: re.search when used within an if/else fails Kevin T <kevinintx@gmail.com> - 2012-11-28 11:39 -0800
                Re: Re: re.search when used within an if/else fails Evan Driscoll <driscoll@cs.wisc.edu> - 2012-11-28 14:08 -0600
                Re: re.search when used within an if/else fails Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-28 21:39 +0000
                Re: re.search when used within an if/else fails Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-11-28 19:20 -0500
                Re: re.search when used within an if/else fails Duncan Booth <duncan.booth@invalid.invalid> - 2012-11-29 09:34 +0000
                Re: re.search when used within an if/else fails Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-11-29 13:38 -0500
                RE: re.search when used within an if/else fails "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-11-29 22:57 +0000
                RE: re.search when used within an if/else fails "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-11-29 22:53 +0000
              Re: re.search when used within an if/else fails Kevin T <kevinintx@gmail.com> - 2012-11-28 11:39 -0800
                Re: re.search when used within an if/else fails Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-28 20:50 +0000
        Re: re.search when used within an if/else fails Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-20 12:39 -0700

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