add stack minimal implementation with tests

Author: ofou

data_structures/stack/stack.py

@@ -0,0 +1,27 @@
+class Stack:
+    """
+    Simple stack implementation using a list
+    """
+
+    def __init__(self) -> None:
+        self.items = []
+
+    def is_empty(self) -> bool:
+        """check if the stack is empty"""
+        return self.items == []
+
+    def push(self, item: any) -> None:
+        """push an item to the top of the stack"""
+        self.items.append(item)
+
+    def pop(self) -> any:
+        """pop the top item of the stack"""
+        return self.items.pop()
+
+    def peek(self) -> any:
+        """peek at the top item of the stack"""
+        return self.items[len(self.items)-1]
+
+    def size(self) -> int:
+        """return the size of the stack"""
+        return len(self.items)

data_structures/stack/stack_test.py

@@ -0,0 +1,44 @@
+import unittest
+from stack import Stack
+
+
+class Test_Stack(unittest.TestCase):
+
+    def test_is_empty(self: any) -> None:
+        stack = Stack()
+        self.assertTrue(stack.is_empty())
+        stack.push(1)
+        self.assertFalse(stack.is_empty())
+
+    def test_push(self):
+        stack = Stack()
+        stack.push(1)
+        self.assertEqual(stack.peek(), 1)
+        stack.push(2)
+        self.assertEqual(stack.peek(), 2)
+
+    def test_pop(self):
+        stack = Stack()
+        stack.push(1)
+        stack.push(2)
+        self.assertEqual(stack.pop(), 2)
+        self.assertEqual(stack.pop(), 1)
+
+    def test_peek(self):
+        stack = Stack()
+        stack.push(1)
+        stack.push(2)
+        self.assertEqual(stack.peek(), 2)
+        self.assertEqual(stack.peek(), 2)
+
+    def test_size(self):
+        stack = Stack()
+        self.assertEqual(stack.size(), 0)
+        stack.push(1)
+        self.assertEqual(stack.size(), 1)
+        stack.push(2)
+        self.assertEqual(stack.size(), 2)
+
+
+if __name__ == '__main__':
+    unittest.main()