Task: Word wrap
C#: namespace RosettaCode.WordWrap
{
    using System;
    using System.Collections.Generic;

    internal static class Program
    {
        private const string LoremIpsum = @"
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas varius sapien
vel purus hendrerit vehicula. Integer hendrerit viverra turpis, ac sagittis arcu
pharetra id. Sed dapibus enim non dui posuere sit amet rhoncus tellus
consectetur. Proin blandit lacus vitae nibh tincidunt cursus. Cum sociis natoque
penatibus et magnis dis parturient montes, nascetur ridiculus mus. Nam tincidunt
purus at tortor tincidunt et aliquam dui gravida. Nulla consectetur sem vel
felis vulputate et imperdiet orci pharetra. Nam vel tortor nisi. Sed eget porta
tortor. Aliquam suscipit lacus vel odio faucibus tempor. Sed ipsum est,
condimentum eget eleifend ac, ultricies non dui. Integer tempus, nunc sed
venenatis feugiat, augue orci pellentesque risus, nec pretium lacus enim eu
nibh.";

        private static void Main()
        {
            foreach (var lineWidth in new[] { 72, 80 })
            {
                Console.WriteLine(new string('-', lineWidth));
                Console.WriteLine(Wrap(LoremIpsum, lineWidth));
            }
        }

        private static string Wrap(string text, int lineWidth)
        {
            return string.Join(string.Empty,
                               Wrap(
                                   text.Split(new char[0],
                                              StringSplitOptions
                                                  .RemoveEmptyEntries),
                                   lineWidth));
        }

        private static IEnumerable<string> Wrap(IEnumerable<string> words,
                                                int lineWidth)
        {
            var currentWidth = 0;
            foreach (var word in words)
            {
                if (currentWidth != 0)
                {
                    if (currentWidth + word.Length < lineWidth)
                    {
                        currentWidth++;
                        yield return " ";
                    }
                    else
                    {
                        currentWidth = 0;
                        yield return Environment.NewLine;
                    }
                }
                currentWidth += word.Length;
                yield return word;
            }
        }
    }
}

Python: >>> import textwrap
>>> help(textwrap.fill)
Help on function fill in module textwrap:

fill(text, width=70, **kwargs)
    Fill a single paragraph of text, returning a new string.
    
    Reformat the single paragraph in 'text' to fit in lines of no more
    than 'width' columns, and return a new string containing the entire
    wrapped paragraph.  As with wrap(), tabs are expanded and other
    whitespace characters converted to space.  See TextWrapper class for
    available keyword args to customize wrapping behaviour.

>>> txt = 
>>> print(textwrap.fill(txt, width=75))
Reformat the single paragraph in 'text' to fit in lines of no more than
'width' columns, and return a new string containing the entire wrapped
paragraph.  As with wrap(), tabs are expanded and other whitespace
characters converted to space.  See TextWrapper class for available keyword
args to customize wrapping behaviour.
>>> print(textwrap.fill(txt, width=45))
Reformat the single paragraph in 'text' to
fit in lines of no more than 'width' columns,
and return a new string containing the entire
wrapped paragraph.  As with wrap(), tabs are
expanded and other whitespace characters
converted to space.  See TextWrapper class
for available keyword args to customize
wrapping behaviour.
>>> print(textwrap.fill(txt, width=85))
Reformat the single paragraph in 'text' to fit in lines of no more than 'width'
columns, and return a new string containing the entire wrapped paragraph.  As with
wrap(), tabs are expanded and other whitespace characters converted to space.  See
TextWrapper class for available keyword args to customize wrapping behaviour.
>>>