code: def zero_pad(seq, left=0, right=0, zero=0.):
    
    for unused in xrange(left):
      yield zero
    for item in seq:
      yield item
    for unused in xrange(right):
      yield zero
docs: Zero padding sample generator (not a Stream!).
  
    Parameters
    ----------
    seq :
      Sequence to be padded.
    left :
      Integer with the number of elements to be padded at left (before).
      Defaults to zero.
    right :
      Integer with the number of elements to be padded at right (after).
      Defaults to zero.
    zero :
      Element to be padded. Defaults to a float zero (0.0).
  
    Returns
    -------
    A generator that pads the given ``seq`` with samples equals to ``zero``,
    ``left`` times before and ``right`` times after it.