Data Structures in Python: Dequeue

A Dequeue is simply a double-ended Queue.

If you don’t know what a Queue is then you must go through the Queue tutorial.

With double-ended what I really mean is that we can append elements from either end (start and end) and remove them from either end (start and end).

To implement this we can use deque from collections module in Python just like we did in Queue.

Adding elements to either end

We can add elements to the left using the ‘appendleft()’ method and to the right using the ‘append()’ method:

from collections import deque
dequeue = deque(['Sun','Mon','Tue'])
dequeue.appendleft('Thu') #Appending to left
print(dequeue)
#OUTPUT
deque(['Thu', 'Sun', 'Mon', 'Tue'])
dequeue.append('Fri') #Appending to right
print(dequeue)
#OUTPUT
deque(['Thu', 'Sun', 'Mon', 'Tue', 'Fri'])

Removing elements to either end

We can remove elements from the left using the ‘popleft()’ method and from the right using the ‘pop()’ method:

from collections import deque
dequeue = deque(['Sun','Mon','Tue'])
dequeue.popleft() #removing from left
print(dequeue)
#OUTPUT
deque(['Sun', 'Mon', 'Tue', 'Fri'])
dequeue.pop() #removing from right
print(dequeue)
#OUTPUT
deque(['Sun', 'Mon', 'Tue'])

That’s it! I hope you understood easily. See you in the next tutorial!

Lectures

Lecture 1: https://medium.com/@saifmdco/data-structures-with-python-introduction-4dadeffa2215

Lecture 2: https://medium.com/@saifmdco/data-structures-with-python-arrays-c498518bf7fd

Lecture 3: https://medium.com/@saifmdco/data-structures-in-python-lists-653a3ad103ab

Lecture 4: https://medium.com/@saifmdco/data-structures-in-python-tuples-3c350640cd9a

Lecture 5: https://medium.com/@saifmdco/data-structures-in-python-dictionary-fad27ffdda8b

Lecture 6: https://medium.com/@saifmdco/data-structures-in-python-2d-array-6bc0154aa717

Lecture 7: https://medium.com/@saifmdco/data-structures-in-python-matrix-22adba5aa597

Lecture 8: https://medium.com/@saifmdco/data-structures-in-python-sets-92d5445e97e8

Lecture 9: https://medium.com/@saifmdco/data-structures-in-python-chainmap-fca2a9d47249

Lecture 10: https://medium.com/@saifmdco/data-structures-in-python-linkedlist-50f2118c659e

Lecture 11: https://medium.com/@saifmdco/data-structures-in-python-stack-6bf182d63581

Lecture 12: https://medium.com/@saifmdco/data-structures-in-python-queue-6361d3dcff0

Lecture 13: https://medium.com/@saifmdco/data-structures-in-python-dequeue-1a585e269a55

Lecture 14: https://medium.com/@saifmdco/data-structures-in-python-custom-stack-b7b9173b4eae

Lecture 15: https://medium.com/@saifmdco/data-structures-in-python-hash-table-39be784eefc1

Lecture 16: https://medium.com/@saifmdco/data-structures-in-python-doubly-linked-list-fe698d74756c