Question

PYTHON - Write and test the following program that meets the following conditions
    -------------------------------------------------------
    write a program that Tests the methods of stack for empty and
    non-empty stacks using the data in 
    is_empty, push, pop, peek
    *Testing pop and peek while empty throws exception
    -------------------------------------------------------
   CONDITIONS
        source - list of data (list of ?)
    RETURNS
        None
   ------------------------------------------------------- 

CODE FOR : Empty, Push, Pop & Peek

def is_empty(self):
  
result = True
if len(self._values) > 0:
result = False
return result

def push(self, value):
  
self._values.append(deepcopy(value))
return

def pop(self):
  
assert len(self._values) > 0, "Cannot pop from an empty stack"
value = self._values.pop()
return value

def peek(self):
assert len(self._values) > 0, "Cannot peek at an empty stack"

value = deepcopy(self._values[-1])
return value

Answer 1

Testing of program

from copy import deepcopy
class stack():

   def __init__(self,stk):
       self._values = stk

   def is_empty(self):
       result = True
       if len(self._values) > 0:
           result = False
       return result

   def push(self, value):
       self._values.append(deepcopy(value))
       return

   def pop(self):
       assert len(self._values) > 0, "Cannot pop from an empty stack"
       value = self._values.pop()
       return value

   def peek(self):
       assert len(self._values) > 0, "Cannot peek at an empty stack"

       value = deepcopy(self._values[-1])
       return value

a = [1,2,3,4]

s = stack(a);
while not s.is_empty():

   print(s.peek())
   s.pop()

s.pop() # This throws exception :

# assert len(self._values) > 0, "Cannot pop from an empty stack"
# AssertionError: Cannot pop from an empty stack

s.peek() # this too throws execption as stack is empty

# assert len(self._values) > 0, "Cannot peek at an empty stack"
# AssertionError: Cannot peek at an empty stack