Shortening strings in python (inspired by standard library textwrap.shorten)

shorten.py

def shorten_end(string, width=80, placeholder=' ...'):
    if len(string) <= width:
        return string
    n2 = width - len(placeholder)
    return string[:n2] + placeholder

def shorten_begin(string, width=80, placeholder='... '):
    if len(string) <= width:
        return string
    n1 = len(string) - width + len(placeholder)
    return placeholder + string[n1:]

def shorten_middle(string, width=80, placeholder=' ... '):
    if len(string) <= width:
        return string
    n2 = int( (width - len(placeholder)) / 2 )
    m1 = - (width - n2 - len(placeholder))
    return string[:n2] + placeholder + string[m1:]


print(shorten_end('nineteen characters', 19))
print(shorten_end('nineteen characters', 18))
print(shorten_end('Much more than nineteen characters', 19))
print('')
# Output:
# nineteen characters
# nineteen chara ...
# Much more than  ...


print(shorten_begin('nineteen characters', 19))
print(shorten_begin('nineteen characters', 18))
print(shorten_begin('Much more than nineteen characters', 19))
print('')
# Output:
# nineteen characters
# ... een characters
# ... teen characters


print(shorten_middle('nineteen characters', 19))
print(shorten_middle('nineteen characters', 18))
print(shorten_middle('Much more than nineteen characters', 19))
# Output:
# nineteen characters
# ninete ... racters
# Much mo ... racters