Added Dequeue in Python

data_structures/Queue/DeQueue.py

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+# Python code to demonstrate working of 
+# extend(), extendleft(), rotate(), reverse()
+
+# importing "collections" for deque operations
+import collections
+
+# initializing deque
+de = collections.deque([1, 2, 3,])
+
+# using extend() to add numbers to right end 
+# adds 4,5,6 to right end
+de.extend([4,5,6])
+
+# printing modified deque
+print ("The deque after extending deque at end is : ")
+print (de)
+
+# using extendleft() to add numbers to left end 
+# adds 7,8,9 to right end
+de.extendleft([7,8,9])
+
+# printing modified deque
+print ("The deque after extending deque at beginning is : ")
+print (de)
+
+# using rotate() to rotate the deque
+# rotates by 3 to left
+de.rotate(-3)
+
+# printing modified deque
+print ("The deque after rotating deque is : ")
+print (de)
+
+# using reverse() to reverse the deque
+de.reverse()
+
+# printing modified deque
+print ("The deque after reversing deque is : ")
+print (de)