Another round based on comments.  I also just noticed that the current doc incorrectly claims that tabs are replaced by *zero* or more spaces.


   Return a copy of the string where all tab characters are replaced by one or
   more spaces, depending on the current column and the given tab size.  Tab
   positions occur every *tabsize* characters (default is 8, giving tab
   positions at columns 0, 8, 16 and so on).  To expand the string, the current
   column is set to zero and the string is examined character by character.  If
   the character is a tab (``\t``), one or more space characters are inserted
   in the result until the current column is equal to the next tab position.
   (The tab character itself is not copied.)  If the character is a newline
   (``\n``) or return (``\r``), it is copied and the current column is reset to
   zero.  Any other character is copied unchanged and the current column is
   incremented by one regardless of how the character is represented when
   printed.

      >>> '01\t012\t0123\t01234'.expandtabs()
      '01      012     0123    01234'
      >>> '01\t012\t0123\t01234'.expandtabs(4)
      '01  012 0123    01234'