simple-linked-list: implement exercise (#1090)

exercises/simple-linked-list/example.py

@@ -0,0 +1,67 @@
+class Node(object):
+    def __init__(self, value):
+        self._value = value
+        self._next = None
+
+    def value(self):
+        return self._value
+
+    def next(self):
+        return self._next
+
+
+class LinkedIterator(object):
+    def __init__(self, linked_list):
+        self.current = linked_list._head
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self.current is None:
+            raise StopIteration
+        value = self.current.value()
+        self.current = self.current.next()
+        return value
+
+    def next(self):
+        return self.__next__()
+
+
+class LinkedList(object):
+    def __init__(self, values=[]):
+        self._head = None
+        self._len = 0
+        [self.push(v) for v in values]
+
+    def __iter__(self):
+        return LinkedIterator(self)
+
+    def __len__(self):
+        return self._len
+
+    def head(self):
+        if self._head is None:
+            raise EmptyListException()
+        return self._head
+
+    def push(self, value):
+        newNode = Node(value)
+        newNode._next = self._head
+        self._head = newNode
+        self._len += 1
+
+    def pop(self):
+        if self._head is None:
+            raise EmptyListException()
+        self._len -= 1
+        ret = self._head.value()
+        self._head = self._head.next()
+        return ret
+
+    def reversed(self):
+        return LinkedList(self)
+
+
+class EmptyListException(Exception):
+    pass