Traversing a nested list to estimate it's shape or dimension

tree-traversal.py

# Shape = 2x3
a = [
        [1, 2, 3],
        [4, 5, 6]
    ]

# Shape = 2x3x2
b = [
        [[1, 1], [2, 2], [3, 3]],
        [[4, 4], [5, 5], [6, 6]]
    ]

# Shape = 3x3x3
c = [
        [[1, 1, 1], [2, 2, 2], [3, 3, 3]],
        [[4, 4, 4], [5, 5, 5], [6, 6, 6]],
        [[7, 7, 7], [8, 8, 8], [9, 9, 9]],
    ]


class Vector():
    def __init__(self, v):
        self.v = v
    
    def __repr__(self):
        return str(self.v)

    def __str__(self):
        return repr(self)
    
    def traverse(self, node):
        """Traverse a tree node."""
        # Retrieve all the element in current node.
        elements = self.getElements(node)
        
        # Append the number of element in current node.
        self._shape.append(len(elements))
        
        # Check if any elements contains a node.
        nodes = list(filter(self.isNode, elements))
        
        # If there's any node.
        if len(nodes) != 0:
            # Loop through the nodes & continue traversal.
            self.traverse(nodes[0])
    
    @staticmethod
    def isNode(element):
        """Determine if an element is a node or vertex.
        Returns True if it's node & False otherwise.
        """
        iterables = {list, tuple, set}
        return type(element) in iterables
    
    @staticmethod
    def getElements(node):
        """Returns the element of a given node."""
        return [element for element in node]
    
    @property
    def shape(self):
        """Retrieve the shape of current vector."""
        # Start of with an empty shape.
        self._shape = []
        
        # Traverse the vector tree.
        self.traverse(self.v)
        
        return self._shape


if __name__ == '__main__':
    vec_a = Vector(a)
    vec_b = Vector(b)
    vec_c = Vector(c)
    
    print('{} = {}'.format('vec_a', vec_a))
    print('{} = {}'.format('vec_b', vec_b))
    print('{} = {}'.format('vec_c', vec_c))
    
    print()
    
    print('Shape for vec_a =', vec_a.shape)
    print('Shape for vec_b =', vec_b.shape)
    print('Shape for vec_c =', vec_c.shape)