switch to f-strings

Some cells were still using str.format. A bunch of the internal
python files also use them, but I care less about that.

02-Discrete-Bayes.ipynb

@@ -581,7 +581,7 @@
     {
      "data": {
       "application/vnd.jupyter.widget-view+json": {
-       "model_id": "2709d4897c90432eabebbcf3aa60113c",
+       "model_id": "c65bc79da49448efb42e0bfd882986e4",
        "version_major": 2,
        "version_minor": 0
       },
@@ -758,7 +758,7 @@
     {
      "data": {
       "application/vnd.jupyter.widget-view+json": {
-       "model_id": "29c7da8c293a43ddb6e34bd840e9971e",
+       "model_id": "67b1c6758fff4724b590d76d758d0de5",
        "version_major": 2,
        "version_minor": 0
       },
@@ -1250,7 +1250,7 @@
     {
      "data": {
       "application/vnd.jupyter.widget-view+json": {
-       "model_id": "f47a87a1ec27474ea864c92a52ce4ac9",
+       "model_id": "30b640471e4c4f91a079e8f32994f7f3",
        "version_major": 2,
        "version_minor": 0
       },
@@ -1303,7 +1303,7 @@
     {
      "data": {
       "application/vnd.jupyter.widget-view+json": {
-       "model_id": "15dde650d59e4ffe88e2163d1220860f",
+       "model_id": "32ba45c576874b9d965aa34b6cbb2002",
        "version_major": 2,
        "version_minor": 0
       },
@@ -1527,9 +1527,8 @@
     "        print()\n",
     "        print('final position is', robot.pos)\n",
     "        index = np.argmax(posterior)\n",
-    "        print('''Estimated position is {} with '''\n",
-    "              '''confidence {:.4f}%:'''.format(\n",
-    "                index, posterior[index]*100))"
+    "        conf = posterior[index]*100\n",
+    "        print(f'Estimated position is {index} with confidence {conf:.4f}')"
    ]
   },
   {
@@ -1558,7 +1557,7 @@
       "        estimated position is 6 with confidence 100.0000%:\n",
       "\n",
       "final position is 6\n",
-      "Estimated position is 6 with confidence 100.0000%:\n"
+      "Estimated position is 6 with confidence 100.0000\n"
      ]
     },
     {
@@ -1607,7 +1606,7 @@
       "        estimated position is 8 with confidence 49.3174%:\n",
       "\n",
       "final position is 7\n",
-      "Estimated position is 8 with confidence 49.3174%:\n"
+      "Estimated position is 8 with confidence 49.3174\n"
      ]
     },
     {