code: def create_url(self, db="", user="genome", host="genome-mysql.cse.ucsc.edu",
          password="", dialect="mysqldb"):
          
          if os.path.exists(db):
              db = "sqlite:///" + db
  
          # Is this a DB URL? If so, use it directly
          if self.db_regex.match(db):
              self.db = self.url = db
              self.dburl = db
              self.user = self.host = self.password = ""
          else:
              self.db = db
              if user == "genome" and host != "genome-mysql.cse.ucsc.edu":
                  import getpass
                  user = getpass.getuser()
              self.host = host
              self.user = user
              self.password = (":" + password) if password else ""
              self.dburl = self.url.format(db=self.db, user=self.user,
                  host=self.host, password=self.password, dialect=dialect)
docs: internal: create a dburl from a set of parameters or the defaults on
          this object