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# 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
# 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])