How to Implement a Python Stack
Introduction to
stacks and Queue data structures, which organized computer storage for
efficient access and manipulation of data.
The stacks and queue
are very simple to learn and execute with ease, and their usage is very common.
Stacks follows the
LIFO principle that is last in first out. The last element will be removed or
pop first.
Two operations are
therein, one is pushed, which adds an element to the top of the stack, and the second one is pop, which removes the element at the top of the stack.
So let us begin with implementing stacks, using lists in python. Let us first create an empty list name[].
We are going to add elements to the
list, name [] using the append () method.
# create an empty list name
name=[]
# add elements into the list with
append method in the list as Stack
name.append('Siraz')
name.append('Dhoni')
name.append('Shami')
name.append('Kholi')
name.append('Rahul')
name.append('Bumrah')
print(name)
Adding elements to the list using the append() method ensures the push operation of the stack.
Now let us try removing elements
from the list.
name.pop()
It will delete the Bumrah as it is
entered last
['Siraz', 'Dhoni', 'Shami', 'Kholi',
'Rahul']
Let us try to delete the item again
from the list for which we have to write the same syntax
name.pop()
The above code deletes Rahul from
the list, and we are left with only
['Siraz', 'Dhoni', 'Shami', 'Kholi']
Stack using deque in python
Implementing push with the help of
append() method of the deque, We have to import deque from python collection
library as follows
# We can initialize a deque with a
list
name = deque()
# Use append like before to add
elements
name.append ('Siraz')
name.append ('Dhoni')
name.append ('Shami')
name.append ('Kholi')
name.append ('Rahul')
name.append ('Bumrah')
so when we print the print(name), it will
print as follows
deque(['Siraz', 'Dhoni', 'Shami',
'Kholi', 'Rahul', 'Bumrah'])
Now using pop() of deque, we can
implement stack pop operation as follows
name.pop()
print (name)
deque(['Siraz', 'Dhoni', 'Shami',
'Kholi', 'Rahul'])
The last element is Bumrah is deleted
first
name.pop()
print (name)
deque(['Siraz', 'Dhoni', 'Shami',
'Kholi'])
The second last element Rahul is
removed second and so on.
Implementation using python queue module
In the Python queue module there is a LIFO
Queue, which is basically nothing but Stack. Element is inserted into the queue
using put() method that act as PUSH and get () remove data out from the queue
that act as POP operation of stack.
from queue import LifoQueue
# Initializing the stack with
maxsize is 10
stack = LifoQueue(maxsize = 10)
# qsize() show the number of
elements
# in the stack
print(“Initial size of ”stack.qsize())
# put() function to push
# element in the stack
stack.put ('Siraz')
stack.put ('Dhoni')
stack.put ('Shami')
stack.put ('Kholi')
stack.put ('Rahul')
stack.put ('Bumrah')
print("Full is over or not :
", stack.full())
print("Total size of the stack:
", stack.qsize())
# This get() method to act as pop
operation of stack in
# LIFO order that is (Last in First
Out)
print ('\nPoped operation from the
stack')
print (stack.get())
print (stack.get())
print (stack.get())
print("\nStack Empty or not :
", stack.empty())
Output
Initial size of 0
Full: False
Size: 6
Elements poped from the stack
Bumrah
Rahul
Kholi
Empty: False
