class SLLStack(object):
def __init__(self):
self.size = 0
self._data = SinglyLinkedList()
def __len__(self):
return self.size
def build(self, list_object):
if not isinstance(list_object, list):
return TypeError('build method only accepts object of type list.')
for i in list_object:
self._data.add_value(i)
self.size += 1
def is_empty(self):
return self.size == 0
def push(self, e):
self.size += 1
self._data.add_value(e)
def pop(self):
if self.is_empty():
raise IndexError("Stack is empty")
top = self._data.head.value
self._data.delete_node(self._data.head)
self.size -= 1
return top
def top(self):
if self.is_empty():
raise IndexError("Stack is empty")
return self._data.head.value
def test_delete_node_method_removes_node_with_given_data():
"""Test that the delete_node method of the Singly Linked List class
removes a Node from the list with the given data."""
ll = SinglyLinkedList()
ll.add_node(1)
ll.delete_node(1)
assert ll.head is None
def test_delete_node_method_reassigns_next_node_to_none_if_deleting_end_Node():
"""Test that the delete_node method of the Singly Linked List correctly
reassigns the next_node to Node if it's removing the last Node of the list
."""
ll = SinglyLinkedList()
ll.add_node(1)
ll.add_node(2)
ll.delete_node(1)
assert ll.head.next_node is None
def test_delete_node_method_reassigns_head_of_list_if_head_is_deleted():
"""Test that the delete_node method of the Singly Linked List class
correctly reassigns the head Node of the list to the next Node if the head
Node is removed."""
ll = SinglyLinkedList()
ll.add_node(1)
ll.add_node(2)
ll.delete_node(2)
assert ll.head.data == 1
def test_delete_node_method_correctly_reassigns_pointers_if_deleting_middle():
"""Test that the delete_node method of the Singly Linked List class
correctly reassigns pointers if deleting a Node that has two Nodes on
either side of it."""
ll = SinglyLinkedList()
for i in range(3):
ll.add_node(i)
ll.delete_node(1)
assert ll.head.data == 2 and ll.head.next_node.data == 0
def test_delete_node_method_raises_exception_if_list_is_empty():
"""Test that the delete_node method of the Singly Linked List class raises
an exception if used on an empty list."""
ll = SinglyLinkedList()
with pytest.raises(LookupError):
assert ll.delete_node(1)
def test_delete_node_method_returns_data_value_of_deleted_node():
"""Test that the delete_node method of the Singly Linked List class returns
the data value of the Node that it deletes."""
ll = SinglyLinkedList()
ll.add_node(1)
assert ll.delete_node(1) == 1
def test_delete_node_raises_exception_if_node_with_given_data_not_in_list():
"""Test that the delete_node method of the Singly Linked List class raises
an exception if no Node with the given data exists in the list."""
ll = SinglyLinkedList()
ll.add_node(1)
with pytest.raises(LookupError):
assert ll.delete_node(5)
