def idFormat(id_num):
    """Format a numeric id into 5-digit string.
    
    Paramters
    ---------
    id_num: str
        A unique string number assigned to a User or Request.    
    """
    
    if len(id_num) == 1:
        id_num = "0000" + id_num
    elif len(id_num) == 2:
        id_num = "000" + id_num
    elif len(id_num) == 3:
        id_num = "00" + id_num
    elif len(id_num) == 4:
        id_num = "0" + id_num
    return id_num