the stack abstract data type stacks are the simplest of all data structuresyet they are also among the most important they are used in host of different applicationsand as tool for many more sophisticated data structures and algorithms formallya stack is an abstract data type (adtsuch that an instance supports the following two methodss push( )add element to the top of stack pop)remove and return the top element from the stack san error occurs if the stack is empty additionallylet us define the following accessor methods for conveniences top)return reference to the top element of stack swithout removing itan error occurs if the stack is empty is empty)return true if stack does not contain any elements len( )return the number of elements in stack sin pythonwe implement this with the special method len by conventionwe assume that newly created stack is emptyand that there is no priori bound on the capacity of the stack elements added to the stack can have arbitrary type example the following table shows series of stack operations and their effects on an initially empty stack of integers operation push( push( len(ss pops is emptys pops is emptys pops push( push( tops push( len(ss pops push( push( popreturn value false true "error stack contents [ [ [ [ [ [[[[ [ [ [ [ [ [ [ [