Add meaningful error handling for non-integer node_ids (was: Solve error) about anastruct HOT 3 CLOSED

class BridgeTruss_b():

    def __init__(self, p, w_tri = 4, h_tri=2, num_tri=6) -> None:
        """
        Calculate displacement of middle point in bridge truss

        Args:
            p (list): list of force applied on the top nodes (N)
            num_tri (int): number of triangles
            disp (bool): display image or not

        """

        self.structure = SystemElements()

        # Triangle coord
        self.x_base = np.arange(0,num_tri+1) * w_tri
        self.x_top = np.arange(0,num_tri) * w_tri + h_tri
        self.y = np.ones(num_tri) * h_tri

        # Create num_tri triangles
        for i in range(num_tri):
            p1 = [self.x_base[i],0]
            p2 = [self.x_top[i], self.y[i]]
            p3 = [self.x_base[i+1],0]
            self.structure.add_element(location=[p1, p2])
            self.structure.add_element(location=[p2, p3])
            self.structure.add_element(location=[p1, p3])
        
        # Create 5 horizontal trusses
        for i in range(num_tri-1):
            self.structure.add_element(location=[[self.x_top[i],self.y[i]], [self.x_top[i+1],self.y[i+1]]])

        # Create support
        self.structure.add_support_fixed(node_id=1)  # Pin support
        self.structure.add_support_fixed(node_id= 2*num_tri+1)  # Roller support

        # Create Load
        loadnode = [4]
        for index, point in enumerate(loadnode):
            self.structure.point_load(node_id=point,Fy=p)
    

    def solve(self, disp=True):
        """solving the truss system

        Args:
            disp (bool, optional): Add option to display the whole results or not. Defaults to True.
        """
        # Solve the truss system
        self.structure.solve()

        if disp is True:
            self.structure.show_axial_force()
            self.structure.show_displacement(factor=1)

if __name__ == "__main__":
    aa = BridgeTruss_b(-1000, num_tri=3)
    aa.solve()

$ python3
>>> num_triangles=3
>>> num_triangles+1+(num_triangles+1)
8
>>> num_triangles+1+(num_triangles+1)/2
6.0
>>> int(num_triangles+1+(num_triangles+1)/2)
6