def balanced_parentheses(paren_str):
"""problem involving applications of stack"""
# filter out all values besides brackets
matches = re.finditer(r'[(){}[\]]+', paren_str)
parsed_iter = itertools.chain.from_iterable(
result.group()
for result in matches)
opening = Stack()
for i in parsed_iter:
if i in ("(", "{", "["):
opening.add(i)
else:
if not opening.isEmpty():
if i == ")" and opening.peek() == "(":
opening.get()
elif i == "}" and opening.peek() == "{":
opening.get()
elif i == "]" and opening.peek() == "[":
opening.get()
else:
return False
else:
return False
return True
def revstringstack(str):
# with stack implemented
stack = Stack()
for char in str:
stack.add(char)
new_str = ''
while not stack.isEmpty():
new_str += stack.get()
return new_str
class TestStack(unittest.TestCase):
@staticmethod
def add_to_structure(self, items):
for i in items:
self.structure.add(i)
def setUp(self):
self.structure = Stack()
def test_structure_isEmpty(self):
self.assertEqual(self.structure.isEmpty(), True)
self.add_to_structure(self, range(3))
self.assertEqual(self.structure.isEmpty(), False)
def test_structure_peek(self):
structure = self.add_to_structure(
self, iter(['people', 'potatoes', 'pansies']))
self.assertEqual(self.structure.peek(), 'pansies')
def test_structure_get_length(self):
structure = self.add_to_structure(self, range(5))
self.assertEqual(self.structure.get_length(), 5)
def test_structure_get(self):
structure = self.add_to_structure(self, range(3))
# test that first in are first out
for i in reversed(range(3)):
self.assertEqual(self.structure.get(), i)
def test_empty_items(self):
# for when get, or peek is called on empty structure
self.assertRaises(EmptyItemsError, lambda: self.structure.get())
self.assertRaises(EmptyItemsError, lambda: self.structure.peek())
