Additional examples

Author: sanketsarang

Lesson 6 - Dict.ipynb

@@ -430,7 +430,41 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Like in the above example, if in the following year we want to increment the age of each person by `1`, we can basically do this as an update operation. We can see that the previous age values of `42` and `38` and respectively revised to `43` and `39`"
+    "Like in the above example, if in the following year we want to increment the age of each person by `1`, we can basically do this as an update operation. We can see that the previous age values of `42` and `38` and respectively revised to `43` and `39`\n",
+    "\n",
+    "## Understanding key and value types\n",
+    "\n",
+    "A dict can essentially store any value. Anything that is an object in Python can be stored as a value in the dict. This includes the fact that even functions can be stored as values. \n",
+    "\n",
+    "Keys of a dict can also be of any object type; but only as long as the object is immutable. A mutable object cannot be stored as a dict. Let's look at some examples. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "{('Tom', 'Mike'): (42, 38), ('Harry', 'Alice'): [40, 36], 'Tom': 43, 'Mike': 39}\n"
+     ]
+    }
+   ],
+   "source": [
+    "dict1 = {('Tom', 'Mike'): (42,38), ('Harry', 'Alice'): [40,36]}\n",
+    "dict1.update(nextYear)\n",
+    "print(dict1)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "In the above example `('Tom', 'Mike')` is the key of the dict and `(42,38)` is the value. In the second record, we have used an array of `[40,36]` instead of a tuple. \n",
+    "\n",
+    "We can use `(42,38)` as a key, but we cannot use `[42,38]` as a key. This is because the first is a tuple and a tuple is immutable, but the second is a list which is mutable. A mutable cannot be used as a key, as the object does not have a definite value; which when changed would require the dict to be completely re-keyed, which would be undesirable. "
    ]
   }
  ],