For another Core Python Programming question, I created a stack class. I then
put the class into a script to test it:
#!/usr/bin/python
class Stack(list):
def isempty(self):
length = len(self)
if length == 0:
return True
else:
return False
def peek(self):
length = len(self)
if length == 0:
return 0
else:
last_index = length - 1
return self[last_index]
def stackpop(self):
length = len(self)
if length == 0:
print "Empty list!"
else:
last_index = length - 1
stackpop_val = self[last_index]
self = self[:last_index]
return stackpop_val
def push(self, value):
return self.append(value)
if __name__ == '__main__':
x = True
stack = Stack()
print "Pick an option to modify stack: "
while x == True:
print "1) Peek at the last value"
print "2) Pop off the last value"
print "3) Push a value on the stack"
print "4) Quit Program"
choice_string = raw_input("Make a choice: ")
try:
choice = int(choice_string)
except ValueError:
sys.exit("Not an integer! Goodbye!")
if choice == 1:
if stack.isempty():
print "Stack is empty"
else:
peek_val = stack.peek()
print peek_val
elif choice == 2:
if "pop" in dir(list):
pop_val = stack.pop()
print pop_val
else:
pop_val = stack.stackpop()
print pop_val
elif choice == 3:
push_val = raw_input("Push this value on stack: ")
stack.push(push_val)
print stack
elif choice == 4:
print "Goodbye!"
x = False
else:
x = False
sys.exit("Wrong response Goodbye!")
According to the question, I should test if the pop() function is available.
If that function is not available, the stack should use a pop() method of my
own design. I think I solved the problem, but I am not sure how to test it
because Python 2.4 is installed on my computer.
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