def join (lst,sep=" "):
    """Takes a list of objects of arbitrary type, plus an optional separator string.  Returns a string in which the 'str' 
     representations of the objects are joined by the separator, whose default value is just a single space."""
    strg = ""
    for i,x in enumerate(lst):
        if (i > 0):
            strg += sep
        strg += str(x)
    return strg