Concat.py

def concat(separator, lst):
    """
    Takes string separator and list of strings and retuns one big string with 
    all the string elements of lst concatenated together, but separated by the 
    string separator.
    This implementation is kinda *functional*.
    Examples:
    concat('...', []) -> ""
    concat('...', ["Test"]) -> "Test"
    concat('+', ["One", "Two", "Three"]) -> "One+Two+Three"
    """
    if len(lst) == 0: return ""
    elif len(lst) == 1: return lst[0]
    else: return lst[0] + separator + concat(separator, lst[1:])