Add factory pattern example

README.md

@@ -13,9 +13,9 @@ For information on the training, see the website
    develop the slides and illustrate concepts.
 1. [`environment.yml`](environment.yml): conda environment file intended to be
    cross-platform.
-   1. [`python_software_engineering_linux64_conda_specs.txt`](python_software_engineering_linux64_conda_specs.txt):
-      conda environment specification file specific for 64-bit Linux to precisely
-      reproduce the environment on which the code was developed.
+1. [`python_software_engineering_linux64_conda_specs.txt`](python_software_engineering_linux64_conda_specs.txt):
+   conda environment specification file specific for 64-bit Linux to precisely
+   reproduce the environment on which the code was developed.
 1. [License](LICENSE): license information for the material in this repository.
 1. [Contributing](CONTRIBUTING.md): information on how to contribute to this
    repository.

source-code/README.md

@@ -20,7 +20,6 @@ was used to develop it.
    programming in Python.
 1. `operators-functools`: illustrates some applications of the `operator`
    and `functools` modules in Python's standard library.
-1. `pyparsing`: illustration of unit testing on real world code.
 1. `typing`: illustrates how to use type annotation in Python, and
    demonstrates `mypy`.
 1. `testing`: illustrates writing unit tests with `unittest` and

source-code/descriptors/typed_property.py

@@ -1,7 +1,9 @@
 #!/usr/bin/env python
 
+import sys
 
-class TypedProperty(object):
+
+class TypedProperty():
 
     def __init__(self, name, type, default=None):
         self._name = '-' + name
@@ -13,8 +15,7 @@ def __get__(self, instance, cls):
 
     def __set__(self, instance, value):
         if not isinstance(value, self._type):
-            raise TypeError('value {0} is not of {1}'.format(value,
-                                                             self._type))
+            raise TypeError(f'value {value} is not of type {self._type}')
         setattr(instance, self._name, value)
 
     def __delete__(self, instance, cls):
@@ -36,12 +37,10 @@ def __init__(self, title=None, author=None, year=None):
             self.year = year
 
     def __str__(self):
-        return '{0}\n  {1}, {2}'.format(self.title, self.author, self.year)
+        return f'{self.title}\n  {self.author}, {self.year}'
 
 
 if __name__ == '__main__':
-    import sys
-
     book1 = Book()
     print('showing defaults:')
     print(str(book1) + '\n')
@@ -54,6 +53,6 @@ def __str__(self):
     try:
         book3 = Book(1984, 'George Orwell', 1948)
     except TypeError as error:
-        sys.stderr.write('### error: {0}\n'.format(error))
+        print(f'### error: {error}', file=sys.stderr)
         sys.exit(1)
     sys.exit(0)

source-code/design-patters/README.md

@@ -6,3 +6,5 @@ Code to illustrate some design patterns in Python.
 
 1. `decorator_design_pattern.ipynb`: notebook that illustrate how decorators
    can be used to change the behaviour of objects.
+1. `factory_design_pattern.ipynb`: notebook illustrating how a factory class
+   can be used to conveniently construct many objects with the same properties.

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
 }

source-code/testing/README.md

@@ -17,3 +17,4 @@ versatile.
     testing per se.  It is mainly intended for contract-based programming
     and one can prevent code to be emitted for asserts by using the
     `-O` optimizatino flag when running the code.
+1. `Newick`: illustration of unit testing on real world code.