Fix textual errors

Author: gjbex

source-code/object-orientation/avoiding_class_hierarchies.ipynb

@@ -1,12 +1,5 @@
 {
  "cells": [
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "# Avoiding class hierarchies"
-   ]
-  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -23,7 +16,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 37,
+   "execution_count": 1,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -34,7 +27,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Duck typing"
+    "# Duck typing"
    ]
   },
   {
@@ -53,7 +46,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -71,7 +64,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -96,7 +89,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -112,7 +105,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 50,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -140,14 +133,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "An alternative way to implement this, and to avoid "
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## Mix-in"
+    "# Mix-in"
    ]
   },
   {
@@ -159,7 +145,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 52,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -176,12 +162,12 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "The `Duck` and `Timer` classes now inherit from `SoundMaker`, but"
+    "The `Duck`, `Timer` and `Dog` classes now inherit from `SoundMaker`, but `Dog` doesn't define its sound attribute."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 54,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -196,7 +182,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 55,
+   "execution_count": 8,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -211,7 +197,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 56,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -225,7 +211,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 58,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -234,7 +220,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 59,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [
     {
@@ -251,19 +237,26 @@
     "    print(f'{type(item)} says {item.make_sound()}')"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Since the `Dog` has no `_sound`, the mix-in method raises an exception."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 60,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
      "name": "stderr",
      "output_type": "stream",
      "text": [
       "Traceback (most recent call last):\n",
-      "  File \"<ipython-input-60-1c825f3b7991>\", line 3, in <module>\n",
+      "  File \"<ipython-input-12-1c825f3b7991>\", line 3, in <module>\n",
       "    print(dog.make_sound())\n",
-      "  File \"<ipython-input-52-918cd6c589ba>\", line 7, in make_sound\n",
+      "  File \"<ipython-input-6-918cd6c589ba>\", line 7, in make_sound\n",
       "    raise ValueError(f'{type(self)} does not make sound')\n",
       "ValueError: <class '__main__.Dog'> does not make sound\n"
      ]
@@ -294,9 +287,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.0"
+   "version": "3.9.5"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }