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Python – Queue.LIFOQueue vs Collections.Deque
  • Difficulty Level : Basic
  • Last Updated : 17 Dec, 2020

Both LIFOQueue and Deque can be used using in-built modules Queue and Collections in Python, both of them are data structures and are widely used, but for different purposes. In this article, we will consider the difference between both Queue.LIFOQueue and Collections.Deque concerning usability, execution time, working, implementation, etc. in Python.

queue.LifoQueue: The module queue provides a LIFO Queue which technically works as a Stack. It is usually used for communication between the different threads in the very same process.

Below is a program which depicts the implementation of Lifo.Queue:

Python3




# Import required module
import queue
 
# Initialize LIFO Queue
LIFOq = queue.LifoQueue(maxsize=3)
 
# qsize() give the maxsize of
# the Queue
print(LIFOq.qsize())
 
# Data Inserted as 5->9->1->7,
# same as Queue
LIFOq.put(1)
LIFOq.put(2)
LIFOq.put(3)
 
# Displaying if the Queue is full
print("Full: ", LIFOq.full())
 
# Displaying size of queue
print("Size: ", LIFOq.qsize())
 
# Data will be accessed in the
# reverse order Reverse of that
# of Queue
print(LIFOq.get())
print(LIFOq.get())
print(LIFOq.get())
 
# Displaying if the queue is empty or not
print("Empty: ", LIFOq.empty())

Output:

0
Full:  True
Size:  3
3
2
1
Empty:  True

collections.deque: Deque (Doubly Ended Queue) in Python is implemented using the module collections. This data structure is mainly used for queues. The FIFO queue mechanism is implemented by append() and popleft(). It’s operations are quite faster as compared to lists.



Below is a program that illustrates the implementation of collections.deque:

Python3




# Import required modules
import collections
 
# Initialize deque
Deque = collections.deque([10, 20, 30])
 
# Using append() to insert element at right end
# Inserts 0 at the end of deque
Deque.append(0)
 
# Printing modified deque
print("The deque after appending at right is:", Deque)
 
# Using appendleft() to insert element at left end
# Inserts 100 at the beginning of deque
Deque.appendleft(100)
 
# Printing modified deque
print("The deque after appending at left is: ", Deque)
 
 
# Using pop() to delete element from right end
# Deletes 0 from the right end of deque
Deque.pop()
 
# Printing modified deque
print("The deque after deleting from right is:", Deque);
 
# Using popleft() to delete element from left end
# Deletes 100 from the left end of deque
Deque.popleft()
 
# Printing modified deque
print("Queue:", Deque)

Output:

The deque after appending at right is: deque([10, 20, 30, 0])
The deque after appending at left is:  deque([100, 10, 20, 30, 0])
The deque after deleting from right is: deque([100, 10, 20, 30])
Queue: deque([10, 20, 30])

Difference between LIFOQueue and Deque:

Sr. no.LIFO QueueDequeue
1It implements stacksIt implements a double-edged queue
2Present in Queue modulePresent in Collections module
3Allows various threads to communicate using queued data or messagesSimply intended to be a data structure
4Fewer features (operations and methods)Large Variety of features (operations and methods)
5Follows Last In First OutFollows Fist In First Out
6Slow operations (long execution time)High operations(very low execution time)
6Not commonly used, usually used for thread communication operations.Mostly used for data structure operations.

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