Stacks are the simplest of all data structures, yet they are also among the most important

creates a new stack that is empty. It needs no parameters and returns an empty stack.

peek() : adds a new item to the top of the stack. It needs the item and returns nothing

pop() : removes the top item from the stack. It needs no parameters and returns the item

tests to see whether the stack is empty. It needs no
parameters and returns a boolean value.

peek() returns the bottom item from the stack but does not remove it. It needs no parameters

size(): returns the number of items on the stack. It needs no parametersand returns an integer

used in many applications, such as the Internet Web browsers history and the “undo” mechanism in Text editors

stack

peek() : adds a new item to the top of the stack. It needs the item and returns nothing. this definition is not true.

The order of insertion is the reverse of the order of removalqueue

Using python list , Stack ADT "push()" is implemented using append (item)

Using python list , Stack ADT "peek()"
is implemented using [len (self.item) +1]

Using python list , Stack ADT "size()" is implemented using " len (self.item) "

Deque is a hybrid linear structure, so it requires the LIFO and FIFO ordering.

deque ()
creates a new empty deque. returns an empty queue

Elements are added at one end called(front)

Elements are removed from the other end(front)

dequeue()
removes the rare item, returns the item.