renamed queue-list.py to queue_list.py to be more consistent with python coding guidelines.

stacks-queues/queue_list.py

@@ -0,0 +1,35 @@
+# Need to avoid naming this queue.py as it will conflict with IPython Notebook
+
+class Node(object):
+    def __init__(self, data):
+        self.data = data
+        self.next = None
+
+class Queue(object):
+    def __init__(self):
+        self.first = None
+        self.last = None
+
+    def enqueue(self, data):
+        node = Node(data)
+        if self.first is None and self.last is None:
+            self.first = node
+            self.last = node
+        else:
+            self.last.next = node
+            self.last = node
+
+    def dequeue(self):
+        # Empty list
+        if self.first is None and self.last is None:
+            return None
+        # Remove only element from a one element list
+        elif self.first == self.last:
+            data = self.first.data
+            self.first = None
+            self.last = None
+            return data
+        else:
+            data = self.first.data
+            self.first = self.first.next
+            return data