def join(ol, separator=','):
    """
        from elist.elist import *
        ol = [1,2,3,4]
        join(ol,separator="-")
    """
    if ol.__len__() == 0:
        return ''
    else:
        pass
    cond = type(ol[0]) == type(b'')
    if cond:
        rslt = b''
    else:
        rslt = ''
    length = ol.__len__()
    for i in range(0, length - 1):
        ele = ol[i]
        if cond:
            pass
        else:
            ele = str(ele)
        rslt = rslt + ele + separator
    if cond:
        rslt = rslt + ol[length - 1]
    else:
        rslt = rslt + str(ol[length - 1])
    return rslt
