pilascolas_en.md

📃 README 📝 Exercises

14. STACK(LIFO) and QUEUE(FIFO)

STACK = Last In First Out, .append() .pop()

There are no STACK in Python, so the best solution to create this abstract STACK would be to create an object using a class, but we will see that later. now we will simulate it this way:

stack = [3,4,5]
stack.append(6) # Remember that append() adds an appendix to the end of the list
stack.append(7)
print(stack)

a = stack.pop() # .pop() extracts the last data from the list and if it is not stored it is lost.
print(a) # This is the last data entered and the first to leave (LIFO)
print(stack)

[3, 4, 5, 6, 7] 7 [3, 4, 5, 6]

QUEUES = First In First Out, from collections import deque

.append() .popleft()

They are container objects of the deque type, they can perform operations in both directions, adding or removing elements. To create a queue in Python we need to import the «deque» class from the «collections» package.

from _collections import deque # First we import the deque class from the collections package
stack = deque() # empty
stack = deque(['Paco','Luis','Alvaro'])
print(stack)

stack.append('Oscar') # we add an element to the queue
print(cola)

stack.popleft() # It will take out the first one in the list....
# and since we haven't stored it, that element will be lost...
print(stack)

deque(['Paco', 'Luis', 'Alvaro']) deque(['Paco', 'Luis', 'Alvaro', 'Oscar']) deque(['Luis', 'Alvaro', 'Oscar'])