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regex help

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  regex help Larry Martell <larry.martell@gmail.com> - 2015-03-13 12:05 -0400
    Re: regex help Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-13 18:10 +0100
    Re: regex help Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-14 11:48 +1100

#87372 — regex help

I need to remove all trailing zeros to the right of the decimal point,
but leave one zero if it's whole number. For example, if I have this:

14S,5.0000000000000000,4.56862745000000,3.7272727272727271,3.3947368421052630,5.7307692307692308,5.7547169811320753,4.9423076923076925,5.7884615384615383,5.137254901960000

I want to end up with:

14S,5.0,4.56862745,3.7272727272727271,3.394736842105263,5.7307692307692308,5.7547169811320753,4.9423076923076925,5.7884615384615383,5.13725490196

I have a regex to remove the zeros:

'0+[,$]', ''

But I can't figure out how to get the 5.0000000000000000 to be 5.0.
I've been messing with the negative lookbehind, but I haven't found
one that works for this.

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#87376

Larry Martell wrote:

> I need to remove all trailing zeros to the right of the decimal point,
> but leave one zero if it's whole number. For example, if I have this:
> 
> 
14S,5.0000000000000000,4.56862745000000,3.7272727272727271,3.3947368421052630,5.7307692307692308,5.7547169811320753,4.9423076923076925,5.7884615384615383,5.137254901960000
> 
> I want to end up with:
> 
> 
14S,5.0,4.56862745,3.7272727272727271,3.394736842105263,5.7307692307692308,5.7547169811320753,4.9423076923076925,5.7884615384615383,5.13725490196
> 
> I have a regex to remove the zeros:
> 
> '0+[,$]', ''
> 
> But I can't figure out how to get the 5.0000000000000000 to be 5.0.
> I've been messing with the negative lookbehind, but I haven't found
> one that works for this.

First of all, I find it unlikely that you really want to solve your problem 
with regular expressions.  Google “X-Y problem”.

Second, if you must use regular expressions, the most simple approach is to 
use backreferences.

Third, you need to show the relevant (Python) code.

<http://www.catb.org/~esr/faqs/smart-questions.html>

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#87398

Larry Martell wrote:

> I need to remove all trailing zeros to the right of the decimal point,
> but leave one zero if it's whole number. 


def strip_zero(s):
    if '.' not in s:
        return s
    s = s.rstrip('0')
    if s.endswith('.'):
        s += '0'
    return s


And in use:

py> strip_zero('-10.2500')
'-10.25'
py> strip_zero('123000')
'123000'
py> strip_zero('123000.0000')
'123000.0'


It doesn't support exponential format:

py> strip_zero('1.2300000e3')
'1.2300000e3'

because it isn't clear what you intend to do under those circumstances.


-- 
Steven

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