fixes

kyclark · kyclark · commit 31bedab5e5ab · 2019-06-05T20:31:35.000-05:00
diff --git a/appendix/truthiness/README.md b/appendix/truthiness/README.md
@@ -1,4 +1,4 @@
-# Truthiness: Boolean Evaluations
+# Truthiness
 
 While it would seem Python has an actual Boolean (Yes/No, True/False) type, this idea can be seriously abused in many odd and confusing ways. First off, there are actual `True` and `False` values:
 
@@ -103,14 +103,14 @@ Great! So let's use that on the other values:
 >>> d.get('bar', 'NA')
 ````
 
-The call for `bar` was weird, but remember that we put an actual `None` as the value:
+The call for `bar` returned nothing because we put an actual `None` as the value:
 
 ````
 >>> type(d.get('bar', 'NA'))
 <class 'NoneType'>
 ````
 
-OK, so we go back to this:
+The key `bar` didn't fail because that key exists in the dictionary. The `dict.get` method only returns the second, default argument *if the key does not exist in the dictionary* which is entirely different from checking the *value* of the key in the dictionary. OK, so we go back to this:
 
 ````
 >>> d.get('bar') or 'NA'
diff --git a/article/discussion.md b/article/discussion.md
@@ -8,7 +8,17 @@ On line 26, we need to figure out whether the `article` should be `a` or `an`. W
 
 We can access the first character of the `word` with `word[0]` which looks the same as how we access the first element of a list. Strings are really list of characters, so this isn't so far-fetched, but we do have to remember that Python, like so many programming languages, starts numbering at `0`, so we often talked about the first element of a list as the "zeroth" element.
 
-To decided if the given word starts with a vowel, we ask if `word[0].lower() in  'aeiou'`. So, to unpack that, `word[0]` returns a one-character-long `str` type which has the method `.lower()` which we call using the parentheses. Without the parens, this would just be the *idea* of the function that returns a lowercased version of the string. Understand that the `word` remains unchanged. The function does not lowercase `word[0]`, it only *returns a lowercase version* of that character.
+To decide if the given word starts with a vowel, we ask is `word[0].lower() in  'aeiou'`. So, to unpack that, `word[0]` returns a one-character-long `str` type which has the method `.lower()` which we call using the parentheses. Without the parens, this would just be the *idea* of the function that returns a lowercased version of the string. Understand that the `word` remains unchanged. The function does not lowercase `word[0]`, it only *returns a lowercase version* of that character.
+
+````
+>>> word = 'APPLE'
+>>> word
+'APPLE'
+>>> word[0].lower()
+'a'
+>>> word
+'APPLE'
+````
 
 The `X in Y` form is a way to ask if element `X` is in the collection `Y`:
 
@@ -23,9 +33,7 @@ True
 False
 ````
 
-So we get the first character of `word` and ask if the lowercased version is in the list of characters `aeiou`. 
-
-The `if` *expression* is different from an `if` *statement*. An expression returns a value, and a statement does not. The `if` expression must have an `else`, but the `if` statement does not have this requirement.  The first value is returned if the predicate (the bit after the `if`) evaluates to `True` in a Boolean context (more on that later), otherwise the last value is returned:
+The `if` *expression* is different from an `if` *statement*. An expression returns a value, and a statement does not. The `if` expression must have an `else`, but the `if` statement does not have this requirement.  The first value is returned if the predicate (the bit after the `if`) evaluates to `True` in a Boolean context (cf. "Truthiness"), otherwise the last value is returned:
 
 ````
 >>> 'Hooray!' if True else 'Shucks!'
diff --git a/book.md b/book.md
@@ -190,7 +190,17 @@ On line 26, we need to figure out whether the `article` should be `a` or `an`. W
 
 We can access the first character of the `word` with `word[0]` which looks the same as how we access the first element of a list. Strings are really list of characters, so this isn't so far-fetched, but we do have to remember that Python, like so many programming languages, starts numbering at `0`, so we often talked about the first element of a list as the "zeroth" element.
 
-To decided if the given word starts with a vowel, we ask if `word[0].lower() in  'aeiou'`. So, to unpack that, `word[0]` returns a one-character-long `str` type which has the method `.lower()` which we call using the parentheses. Without the parens, this would just be the *idea* of the function that returns a lowercased version of the string. Understand that the `word` remains unchanged. The function does not lowercase `word[0]`, it only *returns a lowercase version* of that character.
+To decide if the given word starts with a vowel, we ask is `word[0].lower() in  'aeiou'`. So, to unpack that, `word[0]` returns a one-character-long `str` type which has the method `.lower()` which we call using the parentheses. Without the parens, this would just be the *idea* of the function that returns a lowercased version of the string. Understand that the `word` remains unchanged. The function does not lowercase `word[0]`, it only *returns a lowercase version* of that character.
+
+````
+>>> word = 'APPLE'
+>>> word
+'APPLE'
+>>> word[0].lower()
+'a'
+>>> word
+'APPLE'
+````
 
 The `X in Y` form is a way to ask if element `X` is in the collection `Y`:
 
@@ -205,9 +215,7 @@ True
 False
 ````
 
-So we get the first character of `word` and ask if the lowercased version is in the list of characters `aeiou`. 
-
-The `if` *expression* is different from an `if` *statement*. An expression returns a value, and a statement does not. The `if` expression must have an `else`, but the `if` statement does not have this requirement.  The first value is returned if the predicate (the bit after the `if`) evaluates to `True` in a Boolean context (more on that later), otherwise the last value is returned:
+The `if` *expression* is different from an `if` *statement*. An expression returns a value, and a statement does not. The `if` expression must have an `else`, but the `if` statement does not have this requirement.  The first value is returned if the predicate (the bit after the `if`) evaluates to `True` in a Boolean context (cf. "Truthiness"), otherwise the last value is returned:
 
 ````
 >>> 'Hooray!' if True else 'Shucks!'
@@ -5726,7 +5734,7 @@ positional = "foo" (<class 'str'>)
 
 \newpage
 
-# Appendix 2: Truthiness: Boolean Evaluations
+# Appendix 2: Truthiness
 
 While it would seem Python has an actual Boolean (Yes/No, True/False) type, this idea can be seriously abused in many odd and confusing ways. First off, there are actual `True` and `False` values:
 
@@ -5831,14 +5839,14 @@ Great! So let's use that on the other values:
 >>> d.get('bar', 'NA')
 ````
 
-The call for `bar` was weird, but remember that we put an actual `None` as the value:
+The call for `bar` returned nothing because we put an actual `None` as the value:
 
 ````
 >>> type(d.get('bar', 'NA'))
 <class 'NoneType'>
 ````
 
-OK, so we go back to this:
+The key `bar` didn't fail because that key exists in the dictionary. The `dict.get` method only returns the second, default argument *if the key does not exist in the dictionary* which is entirely different from checking the *value* of the key in the dictionary. OK, so we go back to this:
 
 ````
 >>> d.get('bar') or 'NA'
diff --git a/playful_python.pdf b/playful_python.pdf
