Adds the specified *suffix* to the *subject*. If *replace* is True, the
  old suffix will be removed first. If *suffix* is callable, it must accept
  exactly one argument and return a modified value.

def addsuffix(subject, suffix, replace=False):
  """
  Adds the specified *suffix* to the *subject*. If *replace* is True, the
  old suffix will be removed first. If *suffix* is callable, it must accept
  exactly one argument and return a modified value.
  """

  if not suffix and not replace:
    return subject
  if replace:
    subject = rmvsuffix(subject)
  if suffix and callable(suffix):
    subject = suffix(subject)
  elif suffix:
    subject += suffix
  return subject