def __init__(self, exp):
# DST = Data Structure
self.expressionOperands = LinkedListStack()
self.expressionOperators = LinkedListStack()
self.expected_operators = {'÷': '/', 'x': '*',
'+': '+', '-': '-', '(': '(', ')': ')'}
self.exp = exp
class Expression:
def __init__(self, exp):
# DST = Data Structure
self.expressionOperands = LinkedListStack()
self.expressionOperators = LinkedListStack()
self.expected_operators = {'÷': '/', 'x': '*',
'+': '+', '-': '-', '(': '(', ')': ')'}
self.exp = exp
def evaluate(self):
parsed_expression = self.parse()
for token in parsed_expression:
if token == '(':
continue
elif token == ')':
rightOperand = self.expressionOperands.pop()
leftOperand = self.expressionOperands.pop()
operator = self.expressionOperators.pop()
result = self._performOperation(
leftOperand, rightOperand, operator)
self._save(result, self.expressionOperands)
elif token in self.expected_operators:
token = self.expected_operators[token]
self._save(token, self.expressionOperators)
else:
token = self._convert(token)
self._save(token, self.expressionOperands)
finalResult = self.expressionOperands.pop()
return finalResult
def _convert(self, token):
return float(token) if '.' in token else int(token)
def _performOperation(self, left, right, op):
if op == '+':
result = left + right
elif op == '-':
result = left - right
elif op == '/':
result = left / right
else:
result = left * right
return result
def _save(self, data, stack):
stack.push(data)
def parse(self):
parsed_expression = ['']
for token in self.exp:
last_token = parsed_expression[-1]
if (last_token.isdigit() or '.' in last_token or last_token == '') and (token not in self.expected_operators):
parsed_expression[-1] += token
else:
parsed_expression.append(token)
return parsed_expression[1:]
def setUp(self):
self.n1 = Node(1)
self.n2 = Node(2)
self.n3 = Node(3)
self.stack = LinkedListStack()
self.stack.push(1)
self.stack.push(2)
self.stack.push(self.n1)
def test_size(self):
# empty stack
stack = LinkedListStack()
self.assertEqual(stack.size(), 0)
# one item
stack.push('a')
self.assertEqual(stack.size(), 1)
# +1 item
stack.push('b')
self.assertEqual(stack.size(), 2)
def test_peek(self):
# empty stack
stack = LinkedListStack()
with self.assertRaises(StackException):
stack.peek()
# add one thing then peek. it should still be there
stack.push('a')
self.assertEqual(stack.peek(), 'a')
self.assertEqual(stack.peek(), 'a')
def test_is_empty(self):
# empty stack
stack = LinkedListStack()
self.assertTrue(stack.is_empty())
# non-empty stack
stack.push('a')
self.assertFalse(stack.is_empty())
def test_push(self):
"""
We can push an item on the stack. We should not get an error
"""
stack = LinkedListStack()
# nothing sent it
with self.assertRaises(TypeError):
stack.push()
# add a bunch of items and push. no errors
mixed_list = [1, 'a', [6, 7, 8], {"cat": "sylvester"}, None]
for item in mixed_list:
stack.push(item)
class TestStack(unittest.TestCase):
def setUp(self):
self.n1 = Node(1)
self.n2 = Node(2)
self.n3 = Node(3)
self.stack = LinkedListStack()
self.stack.push(1)
self.stack.push(2)
self.stack.push(self.n1)
def test_peek(self):
item = self.stack.peek()
self.assertEqual(item, self.n1)
def test_push(self):
self.assertEqual(self.stack.get_size(), 3)
self.stack.push(self.n2)
self.assertEqual(self.stack.get_size(), 4)
def test_pop(self):
item = self.stack.pop()
self.assertEqual(item, self.n1)
def test_is_empty(self):
empty_stack = LinkedListStack()
self.assertEqual(empty_stack.is_empty(), True)
self.assertEqual(self.stack.is_empty(), False)
def test_get_size(self):
empty_stack = LinkedListStack()
self.assertEqual(empty_stack.get_size(), 0)
self.assertEqual(self.stack.get_size(), 3)
def test_get_size(self):
empty_stack = LinkedListStack()
self.assertEqual(empty_stack.get_size(), 0)
self.assertEqual(self.stack.get_size(), 3)
def test_is_empty(self):
empty_stack = LinkedListStack()
self.assertEqual(empty_stack.is_empty(), True)
self.assertEqual(self.stack.is_empty(), False)
def setUp(self):
self.stack = LinkedListStack()
class QueueTests(unittest.TestCase):
def setUp(self):
self.stack = LinkedListStack()
def test_len_returns_0_for_empty_stack(self):
self.assertEqual(len(self.stack), 0)
def test_len_returns_correct_length_after_push(self):
self.assertEqual(len(self.stack), 0)
self.stack.push(2)
self.assertEqual(len(self.stack), 1)
self.stack.push(4)
self.assertEqual(len(self.stack), 2)
self.stack.push(6)
self.stack.push(8)
self.stack.push(10)
self.stack.push(12)
self.stack.push(14)
self.stack.push(16)
self.stack.push(18)
self.assertEqual(len(self.stack), 9)
def test_empty_pop(self):
self.assertIsNone(self.stack.pop())
self.assertEqual(len(self.stack), 0)
def test_pop_respects_order(self):
self.stack.push(100)
self.stack.push(101)
self.stack.push(105)
self.assertEqual(self.stack.pop(), 105)
self.assertEqual(len(self.stack), 2)
self.assertEqual(self.stack.pop(), 101)
self.assertEqual(len(self.stack), 1)
self.assertEqual(self.stack.pop(), 100)
self.assertEqual(len(self.stack), 0)
self.assertIsNone(self.stack.pop())
self.assertEqual(len(self.stack), 0)
class TestLinkedListStack(unittest.TestCase):
def setUp(self):
self.stack = LinkedListStack()
def test_push(self):
self.stack.push(1)
self.assertEqual(self.stack.peek(), 1)
def test_pop(self):
popped = self.stack.pop()
self.assertIs(popped, None)
self.stack.push(1)
popped = self.stack.pop()
self.assertEqual(popped, 1)
def test_full_stack(self):
for i in range(10):
self.stack.push(i)
self.assertEqual(self.stack.peek(), 9)
for i in range(10):
self.assertEqual(self.stack.pop(), 9 - i)
self.assertEqual(self.stack.pop(), None)
class TestLinkedListStack(unittest.TestCase):
def setUp(self):
self.st = LinkedListStack()
def tearDown(self):
del self.st
# default feature test - push, pop, peek
def test_01(self):
self.st.push(1)
self.st.push(2)
self.st.push(3)
self.assertEqual(self.st.peek(), 3)
self.assertEqual(self.st.pop(), 3)
self.assertEqual(self.st.peek(), 2)
self.assertEqual(self.st.pop(), 2)
self.assertEqual(self.st.peek(), 1)
self.assertEqual(self.st.pop(), 1)
# raise error when pop with empty stack
def test_02(self):
with self.assertRaises(IndexError) as cm:
self.st.pop()
self.assertEqual("stack is empty", str(cm.exception))
# test check empty
def test_03(self):
self.assertTrue(self.st.is_empty())
def test_pop(self):
"""
We can pop an item from the stack
"""
# empty stack
stack = LinkedListStack()
with self.assertRaises(StackException):
stack.pop()
# add one thing then pop
stack.push('a')
self.assertEqual(stack.pop(), 'a')
with self.assertRaises(StackException):
stack.pop()
# add 3 things then pop
stack.push('a')
stack.push('b')
stack.push('c')
self.assertEqual(stack.pop(), 'c')
self.assertEqual(stack.pop(), 'b')
self.assertEqual(stack.pop(), 'a')
with self.assertRaises(StackException):
stack.pop()
