Initial data commit

Task/Doubly-linked-list-Traversal/Python/doubly-linked-list-traversal-1.py

@@ -0,0 +1,29 @@
+class List:
+    def __init__(self, data, next=None, prev=None):
+        self.data = data
+        self.next = next
+        self.prev = prev
+
+    def append(self, data):
+        if self.next == None:
+            self.next = List(data, None, self)
+            return self.next
+        else:
+            return self.next.append(data)
+
+# Build the list
+tail = head = List(10)
+for i in [ 20, 30, 40 ]:
+    tail = tail.append(i)
+
+# Traverse forwards
+node = head
+while node != None:
+    print(node.data)
+    node = node.next
+
+# Traverse Backwards
+node = tail
+while node != None:
+    print(node.data)
+    node = node.prev

Task/Doubly-linked-list-Traversal/Python/doubly-linked-list-traversal-2.py

@@ -0,0 +1,5 @@
+l = [ 10, 20, 30, 40 ]
+for i in l:
+    print(i)
+for i in reversed(l):    # reversed produces an iterator, so only O(1) memory is used
+    print(i)