'Exception ignored in:' cython extension classes and their `cdef` methods

Question

I have some cython classes, and in their cdef methods, I have assert statements. However, instead of getting an AssertionError that I can catch, for example, I get Exception ignored in: and I cannot catch it (pytest reports this as warnings as well) Moreover, other errors happening (other than the assert one) are not raised and ignored.

As a simple example, let's say I have a Node class called Node.pyx

cdef class Node:
    def __init__(self, ident):
        self.identifier = ident
        self.children = set()
        self.parents = set()

    cdef void add_child(self, Node child):
        self.children.add(child.identifier)
        child.parents.add(self.identifier)

    cdef void add_parent(self, Node parent):
        self.parent.add(parent.identifier)
        parent.children.add(self.identifier)

    cdef void remove_child(self, Node child):
        assert child.identifier in self.children

        self.children.remove(child.identifier)
        child.parents.remove(self.identifier)

    cdef void remove_parent(self, Node parent):
        assert parent.identifier in self.parents

        self.parents.remove(parent.identifier)
        parent.children.remove(self.identifier)

and its corrisponding Node.pxd file

cdef class Node:
    cdef int identifier
    cdef set children
    cdef set parents

    cdef void add_child(self, Node child)
    cdef void add_parent(self, Node parent)
    cdef void remove_child(self, Node child)
    cdef void remove_parent(self, Node parent)

As this is all cdef, it can only be used by another pyx script or function. So let's have another script testing the nodes, node_test.pyx

from Node cimport Node

def test_error_raising():
        cdef Node node1 = Node(1)
        cdef Node node2 = Node(2)

        node1.remove_parent(node2)

Now if I compile all of this with cythonize -i *pyx or a simpel setup script, all compiles well. However, running this test_node.py

from node_test import test_error_raising

try:
    test_error_raising()
except AssertionError:
    print("You have assertion error!")

I get

AssertionError
Exception ignored in: 'Node.Node.remove_parent'
Traceback (most recent call last):
  File "test_node.py", line 5, in <module>
    test_error_raising()
AssertionError:

System and versions:

Distributor ID: Ubuntu
Description:    Ubuntu 20.04.2 LTS

Cython version 0.29.21

Python 3.8.5

Answer 1

See:

https://cython.readthedocs.io/en/latest/src/userguide/language_basics.html#error-return-values

In addition to the above, the useful:

cdef <some_type> some_func() except? -1:

cdef <some_type> some_func() except *:

cdef <some_type> some_func() except +:

forms are described.