def test_stack_exception():
stack = Stack()
exc = "Method not allowed on empty collection."
with pytest.raises(InvalidOperationError) as error1:
stack.peek()
with pytest.raises(InvalidOperationError) as error2:
stack.pop()
assert str(error1.value) == exc and str(error2.value) == exc
class PseudoQueue(object):
# internal stack obj
_data = None
def __init__(self):
# create Stack for internal data-struct
self._data = Stack()
def count(self):
# pass through method to underlying data struct
# BigO == O(n)
return self._data.count()
def enqueue(self, val: str) -> bool:
# enqeue a value at the end queue
# BigO == O(1)
self._data.push(val)
return True
def dequeue(self) -> (str, bool):
# dequeue from head of queue
# BigO == O(n)
# Algo: use a second stack, as we need the bottom element on the first stack
# so we are going to unload the first stack, into a temp stack, in order to
# get at the bottom element of the first, then rebuild it from temp to first-stack
retStr = ''
retBool = False
# Empty List? Early return!
b, s = self._data.peek()
if not b:
return retStr, retBool
# reverse the primary stack into temp stack
tempStack = Stack()
while True:
b, s = self._data.peek()
if b == False:
break
val = self._data.pop()
tempStack.push(val)
# top element on tempstack is the bottom of the primary data stack
retStr = tempStack.pop()
# reverse the temp stack back to the primary stack
while True:
b, s = tempStack.peek()
if b == False:
break
val = tempStack.pop()
self._data.push(val)
return retStr, True
def test_empty_stack():
"""
Exception raised when peeking empty stack.
"""
stack = Stack()
try:
stack.peek()
except EmptyStackException:
assert True
def dequeue(self, pref: AnimalType = None) -> Animal:
# grab animal that has been in queue the longest, optionally provide parameter
# No Pref First
if pref == None:
b, val = self.q.peek()
if not b:
return None
if self.q.dequeue(val):
return Animal.Factory(val)
else:
stack = Stack()
# Find the Animal we Want (deq, push to stack)
found = False
b, val = self.q.peek()
while b:
animal = Animal.Factory(val)
if animal.animaltype == pref:
found = True
break
stack.push(val)
self.q.dequeue(val)
b, val = self.q.peek()
if found:
# Pop off stack and enqueue back to queue
# record the current count, as we need to cycle the enq (back of line) to the front
c = self.q.count()
b, val = stack.peek()
while b:
val = stack.pop()
self.q.enqueue(val)
b, val = stack.peek()
# cycle the back of the list to the front
diff = self.q.count() - c
for x in range(diff):
val = self.q.peek()
self.q.dequeue(val)
self.q.enqueue(val)
return animal
else:
return None
def test_stack_pop():
testing_stack = Stack()
testing_stack.push(1)
testing_stack.push(2)
expected = 2
actual = testing_stack.peek()
assert actual == expected
def test_peek():
test_stack = Stack()
test_stack.push(1)
test_stack.push(2)
test_stack.push(3)
assert test_stack.peek() == 3
def test_pop_one():
stack = Stack()
stack.push(1)
stack.pop()
expected = None
actual = stack.peek()
assert actual == expected
def test_peek():
stack = Stack()
stack.push(1)
stack.push(2)
actual = stack.peek()
expected = 2
assert actual == expected
def test_peek():
s = Stack()
s.push("apple")
s.push("banana")
actual = s.peek()
expected = "banana"
assert actual == expected
def test_peek_empty_exception():
stack = Stack()
stack.push(1)
stack.pop()
actual = stack.peek()
expected = "empty stack"
assert actual == expected
def test_pop_off():
stack = Stack()
stack.push(1)
stack.push(2)
stack.pop()
expected = 1
actual = stack.peek()
assert actual == expected
def test_push_multiple():
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
expected = 3
actual = stack.peek()
assert actual == expected
def test_stack_push():
# STACK: push onto a stack
stack = Stack()
stack.push('pao de queijo')
actualBool, actualStr = stack.peek()
expectedBool, expectedStr = True, 'pao de queijo'
assert actualBool == expectedBool
assert actualStr == expectedStr
def test_stack_push_multiple():
testing_stack = Stack()
testing_stack.push(1)
testing_stack.push(2)
testing_stack.push(3)
expected = 3
actual = testing_stack.peek()
assert actual == expected
def test_stack_peek():
hats = Stack()
hats.push('seahawks')
hats.push('gray')
hats.push('tan')
hats.push('black')
assert hats.peek() == 'black'
def test_push_multiple():
stack = Stack()
stack.push('A')
stack.push('B')
stack.push('C')
expected = 'C'
actual = stack.peek()
assert expected == actual
def dequeue(self) -> (str, bool):
# dequeue from head of queue
# BigO == O(n)
# Algo: use a second stack, as we need the bottom element on the first stack
# so we are going to unload the first stack, into a temp stack, in order to
# get at the bottom element of the first, then rebuild it from temp to first-stack
retStr = ''
retBool = False
# Empty List? Early return!
b, s = self._data.peek()
if not b:
return retStr, retBool
# reverse the primary stack into temp stack
tempStack = Stack()
while True:
b, s = self._data.peek()
if b == False:
break
val = self._data.pop()
tempStack.push(val)
# top element on tempstack is the bottom of the primary data stack
retStr = tempStack.pop()
# reverse the temp stack back to the primary stack
while True:
b, s = tempStack.peek()
if b == False:
break
val = tempStack.pop()
self._data.push(val)
return retStr, True
def test_peek_next_item():
stack = Stack()
stack.push(1)
actual = stack.peek()
expected = 1
assert actual == expected
def test_push_one():
stack = Stack()
stack.push(1)
expected = 1
actual = stack.peek()
assert actual == expected
def test_stack_peek():
testing_stack = Stack()
testing_stack.push('hello')
expected = 'hello'
actual = testing_stack.peek()
assert actual == expected
def test_peek_stack():
stack = Stack()
stack.push('1')
stack.push('2')
assert stack.peek() == '2'
def test_peek_stack():
stack = Stack()
stack.push('works')
assert stack.peek() == 'works'
def test_stack_peek_empty():
hats = Stack()
assert hats.peek() == 'Empty Stack'
def test_peek():
element = Stack()
element.push(1)
assert element.peek() == 1
def test_peek_empty():
s = Stack()
with pytest.raises(InvalidOperationError) as e:
s.peek()
assert str(e.value) == "Method not allowed on empty collection"
def test_exceptions_():
with pytest.raises(Exception):
stack = Stack()
stack.pop()
stack.peek()
def test_Stack_empty():
stack = Stack()
actual = stack.peek()
expected = None
assert actual == expected
def test_stack_peek():
s = Stack()
s.push('1')
s.push('2')
assert s.peek() == '2'
def test_none_peek():
new_stack = Stack()
assert new_stack.peek() == None
