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truncating strings

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  truncating strings Roy Smith <roy@panix.com> - 2011-08-23 09:29 -0700
    Re: truncating strings Chris Rebert <clp2@rebertia.com> - 2011-08-23 10:27 -0700
    Re: truncating strings Seebs <usenet-nospam@seebs.net> - 2011-08-23 20:52 +0000
      Re: truncating strings Ethan Furman <ethan@stoneleaf.us> - 2011-08-23 15:02 -0700
        Re: truncating strings Seebs <usenet-nospam@seebs.net> - 2011-08-23 22:00 +0000
          Re: truncating strings Ethan Furman <ethan@stoneleaf.us> - 2011-08-23 16:44 -0700
            Re: truncating strings Seebs <usenet-nospam@seebs.net> - 2011-08-24 04:21 +0000
          Re: truncating strings Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-24 11:24 +1000

#12101 — truncating strings

I want to log a string but only the first bunch of it, and add "..."
to the end if it got truncated.  This certainly works:

          log_message = message
          if len(log_message) >= 50:
            log_message = log_message[:50] + '...'
          logger.error("FAILED: '%s', '%s', %s, %s" % (log_message,
route, params, e.code))

but it bugs me that there should be some cleaner way to do this.  I'm
fantasizing about something along the lines of:

          logger.error("FAILED: '%s{50}', '%s', %s, %s" % (message,
route, params, e.code))

does anything like this exist?

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#12108

On Tue, Aug 23, 2011 at 9:29 AM, Roy Smith <roy@panix.com> wrote:
> I want to log a string but only the first bunch of it, and add "..."
> to the end if it got truncated.  This certainly works:
>
>          log_message = message
>          if len(log_message) >= 50:
>            log_message = log_message[:50] + '...'
>          logger.error("FAILED: '%s', '%s', %s, %s" % (log_message,
> route, params, e.code))
>
> but it bugs me that there should be some cleaner way to do this.  I'm
> fantasizing about something along the lines of:
>
>          logger.error("FAILED: '%s{50}', '%s', %s, %s" % (message,
> route, params, e.code))
>
> does anything like this exist?

You can specify a maximum width to truncate the string to, but I don't
see any built-in way to add an elision indication (e.g. "...").

>>> "%.4s" % "spam and eggs"
'spam'
>>> "{:.4s}".format("spam and eggs")
'spam'

You could define something to wrap strings and override __format__()
or similar, but that seems like overkill.

Cheers,
Chris
--
http://rebertia.com

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#12116

On 2011-08-23, Roy Smith <roy@panix.com> wrote:
> I want to log a string but only the first bunch of it, and add "..."
> to the end if it got truncated.  This certainly works:

>           logger.error("FAILED: '%s{50}', '%s', %s, %s" % (message,
> route, params, e.code))

> does anything like this exist?

%.50s

-s
-- 
Copyright 2011, all wrongs reversed.  Peter Seebach / usenet-nospam@seebs.net
http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures
http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!
I am not speaking for my employer, although they do rent some of my opinions.

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#12118

Seebs wrote:
> On 2011-08-23, Roy Smith <roy@panix.com> wrote:
>> I want to log a string but only the first bunch of it, and add "..."
>> to the end if it got truncated.  This certainly works:
> 
>>           logger.error("FAILED: '%s{50}', '%s', %s, %s" % (message,
>> route, params, e.code))
> 
>> does anything like this exist?
> 
> %.50s

That's not working in 2.7 or 3.2.

~Ethan~

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#12120

On 2011-08-23, Ethan Furman <ethan@stoneleaf.us> wrote:
> Seebs wrote:
>> On 2011-08-23, Roy Smith <roy@panix.com> wrote:
>>>           logger.error("FAILED: '%s{50}', '%s', %s, %s" % (message,
>>> route, params, e.code))

>>> does anything like this exist?

>> %.50s

> That's not working in 2.7 or 3.2.

Huh.

	Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
	[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
	Type "help", "copyright", "credits" or "license" for more information.
	>>> print "%.5s" % ("hello there, truncate me!")
	hello

-s
-- 
Copyright 2011, all wrongs reversed.  Peter Seebach / usenet-nospam@seebs.net
http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures
http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!
I am not speaking for my employer, although they do rent some of my opinions.

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#12123

Seebs wrote:
> On 2011-08-23, Ethan Furman <ethan@stoneleaf.us> wrote:
>> Seebs wrote:
>>> On 2011-08-23, Roy Smith <roy@panix.com> wrote:
>>>>           logger.error("FAILED: '%s{50}', '%s', %s, %s" % (message,
>>>> route, params, e.code))
> 
>>>> does anything like this exist?
> 
>>> %.50s
> 
>> That's not working in 2.7 or 3.2.
> 
> Huh.
> 
> 	Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
> 	[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
> 	Type "help", "copyright", "credits" or "license" for more information.
> 	>>> print "%.5s" % ("hello there, truncate me!")
> 	hello

Ah -- that's only part of it -- the OP wants '...' to print as well.  :)

~Ethan~

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#12133

On 2011-08-23, Ethan Furman <ethan@stoneleaf.us> wrote:
> Ah -- that's only part of it -- the OP wants '...' to print as well.  :)

Ohhhh.  Hmm.

That's harder.  I can't think of a pretty way, so I think I'd probably
write a "prettytrunc(string, len)" or something similar.

-s
-- 
Copyright 2011, all wrongs reversed.  Peter Seebach / usenet-nospam@seebs.net
http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures
http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!
I am not speaking for my employer, although they do rent some of my opinions.

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#12125

Seebs wrote:

> Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
> [GCC 4.2.1 (Apple Inc. build 5646)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
> >>> print "%.5s" % ("hello there, truncate me!")
> hello


Well, whadda you know, I learned something new :)


In any case, this doesn't solve the OP's problem, as he wants to truncate
the input string, and append '...' if and only if it were truncated.

The right solution is to wrap the functionality in a function. It's not
hard, and is elegant. Not everything needs to be a built-in.

# Untested.
def truncate(s, maxwidth=50):
    if len(s) <= maxwidth:
        return s
    s = s[:maxwidth - 3]
    return s + '...'



-- 
Steven

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