Adds wrap up to this part and link to official Python tutorial

Author: willingc

part-4.ipynb

@@ -1,7 +1,7 @@
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+  "signature": "sha256:7b5c09563e39ddf2ede88b8ff357dcdc654af16292c9c86e3bca2fbf703f64c2"
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@@ -782,6 +782,17 @@
      "metadata": {},
      "outputs": []
     },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Why not always use lists instead of tuples? Tuples use less storage space than a list. So if you are reading 1000s of small records from a file, a tuple can be an efficient way to go.\n",
+      "\n",
+      "A practical learning tip: When learning a new language, there are many new terms and concepts. Sometimes it is helpful to see a bigger picture of how everything comes together. I'm a lover of \"Table of Contents\" since I can scan the big picture and see where something like a tuple fits in. The official Python tutorial has a very good [Table of Contents]( https://docs.python.org/3.4/tutorial/index.html), and I sometimes take 5 minutes to just click and explore something new to me.\n",
+      "\n",
+      "Wow! We've come a long way today. "
+     ]
+    },
     {
      "cell_type": "code",
      "collapsed": false,