class PseudoQueue():
def __init__(self):
self.stack1 = Stack()
self.stack2 = Stack()
def enqueue(self, value):
"""
Args:
value ([int]): [inserts the value to stack1 using FIFO]
"""
self.stack1.push(value)
def dequeue(self):
"""[Return the "first in" value from stack1.]
Returns:
[int/value]: [the first in value from stack1]
"""
while self.stack1.peek():
if self.stack1.top.next == None:
return self.stack1.top.value
else:
temp = self.stack1.pop()
self.stack2.push(temp)
continue
def test_peek():
s = Stack()
s.push("apple")
s.push("banana")
actual = s.peek()
expected = "banana"
assert actual == expected
def test_peek(stack_3_vals):
assert stack_3_vals.peek() == 'd'
assert stack_3_vals.top.value == 'd'
# for Empty stack, we expect an exception
empty = Stack()
assert empty.peek() == 'this is an empty Stack'
def test_peek_empty():
s = Stack()
with pytest.raises(InvalidOperationError) as e:
s.peek()
assert str(e.value) == "Method not allowed on empty collection"