Stack is a linear data structure that follows the Last-In/First-Out (LIFO) principle.

• The last inserted element is removed first
• Insertion operation is called push
• Deletion operation is called pop
• Both operations happen at the top of the stack

Stack Implementations in Python

Python does not have a built-in stack type, but stacks can be implemented using different data structures. Below are some common ways to implement a stack:

1. Using a List: Python lists support stack operations using built-in methods like append() and pop().

• append() adds an element to the top of the stack
• While pop() removes the top element

Example: Here, elements are added to the stack using append() and removed using pop() in LIFO order.

st = []
st.append("a")
st.append("b")
st.append("c")

print(st)
print(st.pop())
print(st.pop())

['a', 'b', 'c']
c
b

2. Using collections.deque: deque class from the collections module provides fast insertion and deletion operations. It supports stack behavior using append() and pop() methods. deque is usually faster than lists for large data operations.

Example: Here, a deque is used to perform stack operations efficiently.

from collections import deque

st = deque()
st.append("a")
st.append("b")
st.append("c")

print(st)
print(st.pop())
print(st.pop())

Output

deque(['a', 'b', 'c'])
c
b

3. Using queue.LifoQueue: LifoQueue from the queue module implements a stack using the LIFO principle. It is thread-safe which makes it useful in multi-threaded programs. However, it is generally slower than lists and deque.

Example: Here, elements are inserted using put() and removed using get().

from queue import LifoQueue

st = LifoQueue()
st.put("a")
st.put("b")
st.put("c")

print(st.get())
print(st.get())

Output

c
b

Related Articles:

• Implement Stack using Queues
• Stack Implementation using Linked List