Overriding the Polygon class fails due to __new__()

[NecPlusIA]

The Polygon class builder is defined as:
def __new__(self, shell=None, holes=None):

When I declare a new class inheriting from it, with a few more arguments, an exception occurs:
TypeError: Polygon.__new__() takes from 1 to 3 positional arguments but 4 were given

For instance, my code could be as simple as:

class MyClass(Polygon):
    def __init__(self, shell, holes, my_param_A, my_param_B):
        self.param_A = my_param_A
        self.param_B = my_param_B

I think the polygon builder should begin by:
def __new__(cls, shell=None, holes=None, *args, **kwargs):
but I'm no expert

(shapely v 2.0.1)

[NecPlusIA]

Update: you can always work around the issue by adding

    def __new__(cls, shell=None, holes=None, *args, **kwargs):
        return Polygon.__new__(cls, shell, holes)

to MyClass

[jorisvandenbossche]

Starting with shapely 2.0, subclassing indeed became more difficult / less supported. See #1698 and #1233 for related issues.

Note that while you might be able to workaround the __new__ issue, I am not sure that other operations and functions will preserve your custom attributes.

[jerygood870208]

I'm designing a Python square class that inherits properties from Shapely's Polygon. Upon initialization, it only requires input of the center point and side length. Here is my code and the error I met, how to deal with it?
shapely 2.0.3 installed via pip

class SquareClass:
    def __init__(self, center, side_length):
        self.center = Point(center)
        self.side_length = side_length
        # Calculate the coordinates of the square's vertices
        half_side = side_length / 2
        x, y = center
        vertices = [(x - half_side, y - half_side),
                    (x + half_side, y - half_side),
                    (x + half_side, y + half_side),
                    (x - half_side, y + half_side)]
        super().__new__(vertices)
    def __new__(cls, shell=None, holes=None, *args, **kwargs):
        return Polygon.__new__(cls, shell, holes)

center = (0, 0)
side_length = 1
square = SquareClass(center, side_length)
print("Square area:", square.area)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

     [16] center = (0, 0)
     [17] side_length = 1
---> [18] SquareClass(center, side_length)
     [19] print("Square area:", square.area)


     [13] def __new__(cls, shell=None, holes=None, *args, **kwargs):
---> [14] return Polygon.__new__(cls, shell, holes)

File  Scripts\StationGA\.venv\lib\site-packages\shapely\geometry\polygon.py:230, in Polygon.__new__(self, shell, holes)
    [228] return shell
    [229] else:
--> [230] shell = LinearRing(shell)
    [232] if holes is not None:
    [233] if len(holes) == 0:
    [234] # shapely constructor cannot handle holes=[]

File Scripts\StationGA\.venv\lib\site-packages\shapely\geometry\polygon.py:93, in LinearRing.__new__(self, coordinates)
     [90] else:
     [91] return [float(c) for c in o]
---> [93] coordinates = np.array([_coords(o) for o in coordinates])
     [94] if not np.issubdtype(coordinates.dtype, np.number):
...
     [89] return o.coords[0]
     [90] else:
---> [91] return [float(c) for c in o]

TypeError: 'int' object is not iterable