Refurbish chapter 02

- streamline text
- streamline example functions
- move section on built-ins to beginning
- add notes on the concept of a callable

02_functions_01_review.ipynb

@@ -67,7 +67,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q3**: What does it mean for a variable to **go out of scope**?"
+    "**Q3**: What does it mean for a variable to go out of **scope**?"
    ]
   },
   {
@@ -95,7 +95,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q5**: Explain the concept of **forwarding** a function **call**."
+    "**Q5**: Explain the concept of **forwarding** a **function call**."
    ]
   },
   {
@@ -119,6 +119,20 @@
     " "
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Q7**: What are **callables**? How do they relate to `function` objects?"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    " "
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -137,7 +151,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q7**: A mere function **call** is just an **expression**."
+    "**Q8**: A mere function **call** is just an **expression**."
    ]
   },
   {
@@ -151,7 +165,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q8**: When using the `import` statement, we need to ensure that the imported attributes do **not** overwrite any already defined variables and functions."
+    "**Q9**: When using the `import` statement, we need to ensure that the imported attributes do *not* overwrite any already defined variables and functions."
    ]
   },
   {
@@ -165,7 +179,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q9:** Functions always have a name by which we can call them."
+    "**Q10:** Functions always have a name by which we can call them."
    ]
   },
   {
@@ -179,7 +193,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q10**: The [standard library](https://docs.python.org/3/library/index.html) is a collection of numerical tools often used in scientific computing, for example, advanced mathematical functions or utilities for simulation."
+    "**Q11**: The [standard library](https://docs.python.org/3/library/index.html) is a collection of numerical tools often used in scientific computing, for example, advanced mathematical functions or utilities for simulation."
    ]
   },
   {

02_functions_02_exercises.ipynb

@@ -32,7 +32,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q1.1**: The [volume of a sphere](https://en.wikipedia.org/wiki/Sphere) is defined as $\\frac{4}{3} * \\pi * r^3$. Calculate this value for $r=10.0$ and round it to 10 digits after the comma. Use the [standard library](https://docs.python.org/3/library/index.html) to obtain a good approximation of $\\pi$."
+    "**Q1**: The [volume of a sphere](https://en.wikipedia.org/wiki/Sphere) is defined as $\\frac{4}{3} * \\pi * r^3$. Calculate this value for $r=10.0$ and round it to 10 digits after the comma. Use the [standard library](https://docs.python.org/3/library/index.html) to obtain a good approximation of $\\pi$."
    ]
   },
   {
@@ -66,7 +66,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q1.2**: Encapsulate the logic into a function `sphere_volume()` that takes one *positional* argument `radius` and one *keyword-only* argument `digits` defaulting to `5`. The volume should be returned as a `float` object under *all* circumstances. Document your work appropriately in a docstring according to [Google's Python Style Guide](https://github.com/google/styleguide/blob/gh-pages/pyguide.md)."
+    "**Q2**: Encapsulate the logic into a function `sphere_volume()` that takes one *positional* argument `radius` and one *keyword-only* argument `digits` defaulting to `5`. The volume should be returned as a `float` object under *all* circumstances. Document your work appropriately in a docstring according to [Google's Python Style Guide](https://github.com/google/styleguide/blob/gh-pages/pyguide.md)."
    ]
   },
   {
@@ -83,7 +83,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q1.3**: Evaluate the function with `radius = 100.0` and 1, 5, 10, 15, and 20 digits respectively."
+    "**Q3**: Evaluate the function with `radius = 100.0` and 1, 5, 10, 15, and 20 digits respectively."
    ]
   },
   {
@@ -144,7 +144,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q1.4**: What observation do you make?"
+    "**Q4**: What observation do you make?"
    ]
   },
   {
@@ -158,7 +158,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q1.5**: Using the [range()](https://docs.python.org/3/library/functions.html#func-range) built-in, write a `for`-loop and calculate the volume of a sphere with `radius = 42.0` for all `digits` from `1` through `20`. Print out each volume on a separate line.\n",
+    "**Q5**: Using the [range()](https://docs.python.org/3/library/functions.html#func-range) built-in, write a `for`-loop and calculate the volume of a sphere with `radius = 42.0` for all `digits` from `1` through `20`. Print out each volume on a separate line.\n",
     "\n",
     "Note: This is the first task where you need to use the built-in [print()](https://docs.python.org/3/library/functions.html#print) function."
    ]
@@ -186,7 +186,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Q1.6**: What lesson do you learn about the `float` type?"
+    "**Q6**: What lesson do you learn about the `float` type?"
    ]
   },
   {

sample_module.py

@@ -15,16 +15,17 @@ be used outside the module with a single underscore "_". This way, we can
 design the code within a module in a modular fashion and only "export" what we
 want.
 
-Here, all three functions internally forward the computation to an internal
-utility function _scaled_average() that contains all the logic common to the
-three functions. Also, we define one _default_scalar variable that is used as
-the default for the scalar parameter in each of the functions.
+Here, all three functions internally forward parts of their computations
+to the utility functions _round_all() and _scaled_average() that contain all
+the logic common to the three functions.
 
 While this example is stylized, it shows how Python modules are often
 designed.
 """
 
-_default_scalar = 1
+def _round_all(numbers):
+    """Internal utility function to round all numbers in a list."""
+    return [round(n) for n in numbers]
 
 
 def _scaled_average(numbers, scalar):
@@ -33,43 +34,43 @@ def _scaled_average(numbers, scalar):
     return scalar * average
 
 
-def average(numbers, *, scalar=_default_scalar):
+def average(numbers, *, scalar=1):
     """Calculate the average of all numbers in a list.
 
     Args:
-        numbers (list): list of numbers; may be integers or floats
-        scalar (float, optional): the scalar that multiplies the
-            average of the even numbers
+        numbers (list of int's/float's): numbers to be averaged;
+            if non-whole numbers are provided, they are rounded
+        scalar (float, optional): multiplies the average; defaults to 1
 
     Returns:
         float: (scaled) average
     """
-    return _scaled_average(numbers, scalar)
+    return _scaled_average(_round_all(numbers), scalar)
 
 
-def average_evens(numbers, *, scalar=_default_scalar):
+def average_evens(numbers, *, scalar=1):
     """Calculate the average of all even numbers in a list.
 
     Args:
-        numbers (list): list of numbers; may be integers or floats
-        scalar (float, optional): the scalar that multiplies the
-            average of the even numbers
+        numbers (list of int's/float's): numbers to be averaged;
+            if non-whole numbers are provided, they are rounded
+        scalar (float, optional): multiplies the average; defaults to 1
 
     Returns:
         float: (scaled) average
     """
-    return _scaled_average([n for n in numbers if n % 2 == 0], scalar)
+    return _scaled_average([n for n in _round_all(numbers) if n % 2 == 0], scalar)
 
 
-def average_odds(numbers, *, scalar=_default_scalar):
+def average_odds(numbers, *, scalar=1):
     """Calculate the average of all odd numbers in a list.
 
     Args:
-        numbers (list): list of numbers; may be integers or floats
-        scalar (float, optional): the scalar that multiplies the
-            average of the even numbers
+        numbers (list of int's/float's): numbers to be averaged;
+            if non-whole numbers are provided, they are rounded
+        scalar (float, optional): multiplies the average; defaults to 1
 
     Returns:
         float: (scaled) average
     """
-    return _scaled_average([n for n in numbers if n % 2 != 0], scalar)
+    return _scaled_average([n for n in _round_all(numbers) if n % 2 != 0], scalar)