Truncate a string without ending in the middle of a word

I am looking for a way to truncate a string in Python that will not cut off the string in the middle of a word.

For example:

Original:          "This is really awesome."
"Dumb" truncate:   "This is real..."
"Smart" truncate:  "This is really..."

I'm looking for a way to accomplish the "smart" truncate from above.

I actually wrote a solution for this on a recent project of mine. I've compressed the majority of it down to be a little smaller.

def smart_truncate(content, length=100, suffix='...'):
    if len(content) <= length:
        return content
    else:
        return ' '.join(content[:length+1].split(' ')[0:-1]) + suffix

What happens is the if-statement checks if your content is already less than the cutoff point. If it's not, it truncates to the desired length, splits on the space, removes the last element (so that you don't cut off a word), and then joins it back together (while tacking on the '...').

Here's a slightly better version of the last line in Adam's solution:

return content[:length].rsplit(' ', 1)[0]+suffix

(This is slightly more efficient, and returns a more sensible result in the case there are no spaces in the front of the string.)