AtsushiSakai/PythonRobotics · error · TypeError

robot_type must be an instance of RobotType

Error message

robot_type must be an instance of RobotType

What it means

Raised by the robot_type property setter on Config when assigned a value that is not a RobotType enum instance. The config enforces type safety because downstream DWA logic branches on the specific robot type.

Source

Thrown at PathPlanning/DynamicWindowApproach/dynamic_window_approach.py:88

                            [5.0, 9.0],
                            [8.0, 9.0],
                            [7.0, 9.0],
                            [8.0, 10.0],
                            [9.0, 11.0],
                            [12.0, 13.0],
                            [12.0, 12.0],
                            [15.0, 15.0],
                            [13.0, 13.0]
                            ])

    @property
    def robot_type(self):
        return self._robot_type

    @robot_type.setter
    def robot_type(self, value):
        if not isinstance(value, RobotType):
            raise TypeError("robot_type must be an instance of RobotType")
        self._robot_type = value


config = Config()


def motion(x, u, dt):
    """
    motion model
    """

    x[2] += u[1] * dt
    x[0] += u[0] * math.cos(x[2]) * dt
    x[1] += u[0] * math.sin(x[2]) * dt
    x[3] = u[0]
    x[4] = u[1]

    return x

View on GitHub (pinned to 1fe4fb980f)

Solutions

  1. Assign the enum: from dynamic_window_approach import RobotType; config.robot_type = RobotType.cycle.
  2. Convert loaded strings: RobotType[value_str] or RobotType(value_str).
  3. Keep config serialization/deserialization enum-aware (e.g. save .value, load by name).

Example fix

# before
config.robot_type = 'diff'  # string

# after
config.robot_type = RobotType.diff
Defensive patterns

Strategy: type-guard

Validate before calling

from PathPlanning.DynamicWindowApproach.dynamic_window_approach import RobotType
assert isinstance(cfg_value, RobotType) or cfg_value in [m.value for m in RobotType]

Type guard

from PathPlanning.DynamicWindowApproach.dynamic_window_approach import RobotType

def to_robot_type(v):
    return v if isinstance(v, RobotType) else RobotType[v] if v in RobotType.__members__ else RobotType(v)

Prevention

When it happens

Trigger: Assigning config.robot_type = 'omnidirectional' (string) or config.robot_type = 1 instead of a RobotType member like RobotType.cycle.

Common situations: Loading config values from YAML/JSON where enums deserialize as strings, or porting config code that previously used plain strings.

Related errors

AI-assisted analysis of AtsushiSakai/PythonRobotics@1fe4fb980f (2026-08-28). Data as JSON: /api/errors/9f245ea82f6be30d. Report an issue: GitHub.