DragModel

def __init__(
    self,
    bc: float,
    drag_table: DragTableDataType,
    weight: Union[float, Weight] = 0,
    diameter: Union[float, Distance] = 0,
    length: Union[float, Distance] = 0,
) -> None:
    """Initialize a drag model with ballistic coefficient and drag table.

    Args:
        bc: Ballistic coefficient
        drag_table: Either list of DragDataPoint objects or list of
                    dictionaries with 'Mach' and 'CD' keys
        weight: Projectile weight in grains (default: 0)
        diameter: Projectile diameter in inches (default: 0)
        length: Projectile length in inches (default: 0)

    Examples:
        ```python
        # Constant drag curve with C_d = 0.3:
        dm = DragModel(1, [DragDataPoint(1, 0.3)])

        from py_ballisticcalc.drag_tables import TableG7
        # Standard 155gr OTM bullet:
        dm = DragModel(0.23, TableG7, weight=155, diameter=0.308, length=1.2)
        ```

    Raises:
        ValueError: If BC is not positive or drag_table is empty
        TypeError: If drag_table format is invalid
    """
    if len(drag_table) <= 0:
        raise ValueError("Received empty drag table")
    if bc <= 0:
        raise ValueError("Ballistic coefficient must be positive")

    self.drag_table = make_data_points(drag_table)

    if len(self.drag_table) < 2:
        # Add second point with constant C_d to avoid interpolator complaints
        self.drag_table.append(DragDataPoint(self.drag_table[0].Mach + 0.1, self.drag_table[0].CD))

    self.BC = bc
    self.length = PreferredUnits.length(length)
    self.weight = PreferredUnits.weight(weight)
    self.diameter = PreferredUnits.diameter(diameter)
    if weight > 0 and diameter > 0:
        self.sectional_density = self._get_sectional_density()
        self.form_factor = self._get_form_factor(self.BC)

def __init__(self, BC: float, Mach: Optional[float] = None, V: Optional[Union[float, Velocity]] = None) -> None:
    """Initialize a BCPoint.

    Args:
        BC: Ballistic coefficient (must be positive)
        Mach: Mach number (optional, mutually exclusive with `V`)
        V: Velocity (optional, mutually exclusive with `Mach`)

    Raises:
        ValueError: If `BC` is not positive, or if both or neither of `Mach` and `V` are specified.
    """
    if BC <= 0:
        raise ValueError("Ballistic coefficient must be positive")
    if Mach and V:
        raise ValueError("You cannot specify both 'Mach' and 'V' at the same time")
    if not Mach and not V:
        raise ValueError("One of 'Mach' and 'V' must be specified")

    self.BC = BC
    self.V = PreferredUnits.velocity(V or 0)
    if V:
        self.Mach = (self.V >> Velocity.MPS) / self._machC()
    elif Mach:
        self.Mach = Mach