truncating strings

[Roy Smith]

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?

 

[Chris Rebert]

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. "...").
'spam'

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

Cheers,
Chris

 

[Seebs]

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

 

[Seebs]

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.hello

-s

 

[Ethan Furman]

%.50s

That's not working in 2.7 or 3.2.

~Ethan~

 

[Ethan Furman]

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~

 

[Steven D'Aprano]

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.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 + '...'

 

[Seebs]

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