Deque in Python

Deque in Python

Deque can be implemented in python using the module “collections“. Deque is preferred over list in the cases where we need quicker append and pop operations from both the ends of container, as deque provides an O(1) time complexity for append and pop operations as compared to list which provides O(n) time complexity.

Operations on deque :

1. append() :- This function is used to insert the value in its argument to the right end of deque.

2. appendleft() :- This function is used to insert the value in its argument to the left end of deque.

3. pop() :- This function is used to delete an argument from the right end of deque.

4. popleft() :- This function is used to delete an argument from the left end of deque.

Example 1:

# Python code to demonstrate working of  
# append(), appendleft(), pop(), and popleft() 
  
# importing "collections" for deque operations 
import collections 
  
# initializing deque 
de = collections.deque([1,2,3]) 
  
# using append() to insert element at right end  
# inserts 4 at the end of deque 
de.append(4) 
  
# printing modified deque 
print ("The deque after appending at right is : ") 
print (de) 
  
# using appendleft() to insert element at right end  
# inserts 6 at the beginning of deque 
de.appendleft(6) 
  
# printing modified deque 
print ("The deque after appending at left is : ") 
print (de) 
  
# using pop() to delete element from right end  
# deletes 4 from the right end of deque 
de.pop() 
  
# printing modified deque 
print ("The deque after deleting from right is : ") 
print (de) 
  
# using popleft() to delete element from left end  
# deletes 6 from the left end of deque 
de.popleft() 
  
# printing modified deque 
print ("The deque after deleting from left is : ") 
print (de) 

Output:

The deque after appending at right is :

deque([1, 2, 3, 4])

The deque after appending at left is :

deque([6, 1, 2, 3, 4])

The deque after deleting from right is :

deque([6, 1, 2, 3])

The deque after deleting from left is :

deque([1, 2, 3])