diff --git a/.gitignore b/.gitignore
index ad46379..981b13d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,5 @@ __pycache__/
 .DS_Store
 .vscode
 venv
+.venv
 .idea/*
diff --git a/README.md b/README.md
index c88387e..06929d4 100755
--- a/README.md
+++ b/README.md
@@ -2,6 +2,8 @@
 
 In this code repository you find the solutions and sample implementations for the solutions and challenges posed in our [Python Basics](https://realpython.com/products/python-basics-book/) book. All solutions and sample files are ordered by chapter so you can quickly navigate to the code you're looking for.
 
+In most cases, the solutions presented here represent just one way out of many that the exercises and challenges can be solved. If you find a better way to solve one of the exercises or challenges feel free to open an issue or pull request!
+
 ## Get the Book
 
 [» Click here to learn more about the book and get your copy](https://realpython.com/products/python-basics-book/)
@@ -32,4 +34,4 @@ hello
 hi
 ```
 
-> **Note:** Depending on your installation, you may need to type `python3.7` or `python37` to run the examples.
+> **Note:** Depending on your installation, you may need to type `python3.9` or `python39` to run the examples.
diff --git a/ch04-strings-and-string-methods/3-manipulate-strings-with-methods.py b/ch04-strings-and-string-methods/3-manipulate-strings-with-methods.py
index a37fed6..79b6279 100644
--- a/ch04-strings-and-string-methods/3-manipulate-strings-with-methods.py
+++ b/ch04-strings-and-string-methods/3-manipulate-strings-with-methods.py
@@ -27,7 +27,7 @@
 string3 = "  Cheeseburger   "
 
 print(string1.strip())  # Could also use .lstrip()
-print(string1.strip())  # Could also use .rstrip()
+print(string2.strip())  # Could also use .rstrip()
 print(string3.strip())
 
 
diff --git a/ch04-strings-and-string-methods/5-challenge-pick-apart-your-users-input.py b/ch04-strings-and-string-methods/5-challenge-pick-apart-your-users-input.py
index c045b1b..2079edd 100644
--- a/ch04-strings-and-string-methods/5-challenge-pick-apart-your-users-input.py
+++ b/ch04-strings-and-string-methods/5-challenge-pick-apart-your-users-input.py
@@ -6,4 +6,4 @@
 
 user_input = input("Tell me your password: ")
 first_letter = user_input[0]
-print("The first letter you entered was:", first_letter.upper())
+print("The first letter you entered was: " + first_letter.upper())
diff --git a/ch04-strings-and-string-methods/6-working-with-strings-and-numbers.py b/ch04-strings-and-string-methods/6-working-with-strings-and-numbers.py
index 10c2a23..9b4ca3a 100644
--- a/ch04-strings-and-string-methods/6-working-with-strings-and-numbers.py
+++ b/ch04-strings-and-string-methods/6-working-with-strings-and-numbers.py
@@ -28,9 +28,9 @@
 
 
 # Exercise 4
-# Get two numbers from the user, multiple them,
+# Get two numbers from the user, multiply them,
 # and display the result
 a = input("Enter a number: ")
 b = input("Enter another number: ")
 product = float(a) * float(b)
-print("The product of " + a + " and " + b + " is " + str(product))
+print("The product of " + a + " and " + b + " is " + str(product) + ".")
diff --git a/ch04-strings-and-string-methods/7-streamline-your-print-statements.py b/ch04-strings-and-string-methods/7-streamline-your-prints.py
similarity index 81%
rename from ch04-strings-and-string-methods/7-streamline-your-print-statements.py
rename to ch04-strings-and-string-methods/7-streamline-your-prints.py
index 18c29c4..d89832c 100644
--- a/ch04-strings-and-string-methods/7-streamline-your-print-statements.py
+++ b/ch04-strings-and-string-methods/7-streamline-your-prints.py
@@ -1,4 +1,4 @@
-# 4.7 - Streamline Your Print Statements
+# 4.7 - Streamline Your Prints
 # Solutions to review exercies
 
 
@@ -6,7 +6,7 @@
 weight = 0.2
 animal = "newt"
 
-# Concatenate a number and a string in one print statement
+# Concatenate a number and a string in one print call
 print(str(weight) + " kg is the weight of the " + animal + ".")
 
 
diff --git a/ch06-functions-and-loops/2-write-your-own-functions.py b/ch06-functions-and-loops/2-write-your-own-functions.py
index d21c159..ac29db5 100644
--- a/ch06-functions-and-loops/2-write-your-own-functions.py
+++ b/ch06-functions-and-loops/2-write-your-own-functions.py
@@ -5,7 +5,7 @@
 # Exercise 1
 def cube(num):
     """Return the cube of the input number."""
-    cube_num = num ** 3  # Could also use pow(num, 3)
+    cube_num = num**3  # Could also use pow(num, 3)
     return cube_num
 
 
diff --git a/ch06-functions-and-loops/5-challenge-track-your-investments.py b/ch06-functions-and-loops/5-challenge-track-your-investments.py
index 98964f7..0041382 100644
--- a/ch06-functions-and-loops/5-challenge-track-your-investments.py
+++ b/ch06-functions-and-loops/5-challenge-track-your-investments.py
@@ -6,6 +6,7 @@
 
 
 def invest(amount, rate, years):
+    """Display year on year growth of an initial investment"""
     for year in range(1, years + 1):
         amount = amount * (1 + rate)
         print(f"year {year}: ${amount:,.2f}")
diff --git a/ch08-conditional-logic/2-add-some-logic.py b/ch08-conditional-logic/2-add-some-logic.py
index 2880c21..e7bd650 100644
--- a/ch08-conditional-logic/2-add-some-logic.py
+++ b/ch08-conditional-logic/2-add-some-logic.py
@@ -1,14 +1,14 @@
 # 8.2 - Add Some Logic
 # Solutions to review exercises
 
-# --- Exercise 1
+# Exercise 1
 # Test whether these expressions are True or False
 print((1 <= 1) and (1 != 1))
 print(not (1 != 2))
 print(("good" != "bad") or False)
 print(("good" != "Good") and not (1 == 1))
 
-# --- Exercise 2
+# Exercise 2
 # Add parentheses so that the following expressions all
 # evaluate to True
 
diff --git a/ch08-conditional-logic/3-control-the-flow-of-your-program.py b/ch08-conditional-logic/3-control-the-flow-of-your-program.py
index 2f19b72..6e81837 100644
--- a/ch08-conditional-logic/3-control-the-flow-of-your-program.py
+++ b/ch08-conditional-logic/3-control-the-flow-of-your-program.py
@@ -2,6 +2,7 @@
 # Solutions to review exercises
 
 
+# Exercise 1
 # Display whether the length of user input is <, > or = 5 characters
 
 my_input = input("Type something: ")
@@ -12,3 +13,15 @@
     print("Your input is greater than 5 characters long.")
 else:
     print("Your input is 5 characters long.")
+
+
+# Exercise 2
+# Number guessing program ("guess" the number 3)
+
+print("I'm thinking of a number between 1 and 10. Guess which one.")
+my_guess = input("Type in your guess: ")
+
+if my_guess == "3":
+    print("You win!")
+else:
+    print("You lose.")
diff --git a/ch08-conditional-logic/6-recover-from-errors.py b/ch08-conditional-logic/6-recover-from-errors.py
index 157536d..250144b 100644
--- a/ch08-conditional-logic/6-recover-from-errors.py
+++ b/ch08-conditional-logic/6-recover-from-errors.py
@@ -15,7 +15,7 @@
 
 
 # Exercise 2
-# Print character and specifid index in string
+# Print character and specified index in string
 
 input_string = input("Enter a string: ")
 
diff --git a/ch08-conditional-logic/7-simulate-events-and-calculate-probabilities.py b/ch08-conditional-logic/7-simulate-events-and-calculate-probabilities.py
index 29de41f..d7b939f 100644
--- a/ch08-conditional-logic/7-simulate-events-and-calculate-probabilities.py
+++ b/ch08-conditional-logic/7-simulate-events-and-calculate-probabilities.py
@@ -6,7 +6,7 @@
 
 
 # Exercise 1
-# Write a function that simulatee the roll of a die.
+# Write a function that simulates the roll of a die.
 def roll():
     """Return random integer between 1 and 6"""
     return randint(1, 6)
diff --git a/ch08-conditional-logic/8b-challenge-simulate-a-coin-toss-experiment.py b/ch08-conditional-logic/8b-challenge-simulate-a-coin-toss-experiment.py
index a01a8ce..9f3effe 100644
--- a/ch08-conditional-logic/8b-challenge-simulate-a-coin-toss-experiment.py
+++ b/ch08-conditional-logic/8b-challenge-simulate-a-coin-toss-experiment.py
@@ -31,7 +31,7 @@ def coin_flip():
     first_flip = coin_flip()
     flips = flips + 1
     # Continue flipping the coin and updating the tally until
-    # a different result is returned by coin_flips()
+    # a different result is returned by coin_flip()
     while coin_flip() == first_flip:
         flips = flips + 1
     # Increment the flip tally once more to account for the
diff --git a/ch08-conditional-logic/8c-challenge-simulate-a-coin-toss-experiment.py b/ch08-conditional-logic/8c-challenge-simulate-a-coin-toss-experiment.py
index a652fbb..753e91d 100644
--- a/ch08-conditional-logic/8c-challenge-simulate-a-coin-toss-experiment.py
+++ b/ch08-conditional-logic/8c-challenge-simulate-a-coin-toss-experiment.py
@@ -12,26 +12,38 @@
 # 4. After the first toss, you'll need another loop to keep flipping while you
 #    get the same result as the first flip.
 
-from random import randint
+import random
 
 
 def single_trial():
-    toss = randint(0, 1)
-    total_flips = 1
+    """Simulate repeatedly flipping a coin until both heads and tails are seen."""
+    # This function uses random.randint() to simulate a single coin toss.
+    # randint(0, 1) randomly returns 0 or 1 with equal probability. We can
+    # use 0 to represent heads and 1 to represent tails.
 
-    while toss == randint(0, 1):
-        total_flips += 1
-        toss = randint(0, 1)
+    # Flip the coin the first time
+    flip_result = random.randint(0, 1)
+    # Keep a tally of how many times the coin has been flipped. We've only
+    # flipped once so the initial count is 1.
+    flip_count = 1
 
-    total_flips += 1
-    return total_flips
+    # Continue to flip the coin until randint(0, 1) returns something
+    # different than the original flip_result
+    while flip_result == random.randint(0, 1):
+        flip_count = flip_count + 1
+
+    # The last step in the loop flipped the coin but didn't update the tally,
+    # so we need to increase the flip_count by 1
+    flip_count = flip_count + 1
+    return flip_count
 
 
 def flip_trial_avg(num_trials):
+    """Calculate the average number of flips per trial over num_trials total trials."""
     total = 0
     for trial in range(num_trials):
-        total += single_trial()
+        total = total + single_trial()
     return total / num_trials
 
 
-print(f"The average number of coin flips was {flip_trial_avg(10000)}")
+print(f"The average number of coin flips was {flip_trial_avg(10_000)}")
diff --git a/ch08-conditional-logic/9a-challenge-simulate-an-election.py b/ch08-conditional-logic/9a-challenge-simulate-an-election.py
index 5d6f04d..a9ef523 100644
--- a/ch08-conditional-logic/9a-challenge-simulate-an-election.py
+++ b/ch08-conditional-logic/9a-challenge-simulate-an-election.py
@@ -10,7 +10,7 @@
 num_times_B_wins = 0
 
 num_trials = 10_000
-for trial in range(0,num_trials):
+for trial in range(0, num_trials):
     votes_for_A = 0
     votes_for_B = 0
 
@@ -26,7 +26,7 @@
     else:
         votes_for_B = votes_for_B + 1
 
-    # Determine who wins the erd region
+    # Determine who wins the 3rd region
     if random() < 0.17:
         votes_for_A = votes_for_A + 1
     else:
diff --git a/ch08-conditional-logic/9b-challenge-simulate-an-election.py b/ch08-conditional-logic/9b-challenge-simulate-an-election.py
index 63364f3..eb45794 100644
--- a/ch08-conditional-logic/9b-challenge-simulate-an-election.py
+++ b/ch08-conditional-logic/9b-challenge-simulate-an-election.py
@@ -37,7 +37,8 @@ def run_election(regional_chances):
     # "B" is the total number of regions minus the number of regions won by
     # candidate "A". The total number of regions is the same as the length
     # of the regional_chances list.
-    if num_regions_won_by_A > len(regional_chances) - num_regions_won_by_A:
+    num_regions_won_by_B = len(regional_chances) - num_regions_won_by_A
+    if num_regions_won_by_A > num_regions_won_by_B:
         return "A"
     else:
         return "B"
@@ -55,5 +56,5 @@ def run_election(regional_chances):
 # Display the probabilities that candidate A or candidate B wins the
 # election. Note the probability that B wins can be calculated by
 # subtracting the probability that A wins from 1.
-print(f"Probability A wins: {num_times_A_wins / num_trials}")
-print(f"Probability B wins: {1 - (num_times_A_wins / num_trials)}")
+print(f"Probability A wins: {num_times_A_wins / NUM_TRIALS}")
+print(f"Probability B wins: {1 - (num_times_A_wins / NUM_TRIALS)}")
diff --git a/ch09-lists-tuples-and-dictionaries/1-tuples-are-immutable-sequences.py b/ch09-lists-tuples-and-dictionaries/1-tuples-are-immutable-sequences.py
index 96d6ad8..1b0bcf0 100644
--- a/ch09-lists-tuples-and-dictionaries/1-tuples-are-immutable-sequences.py
+++ b/ch09-lists-tuples-and-dictionaries/1-tuples-are-immutable-sequences.py
@@ -13,7 +13,7 @@
 
 
 # Exercise 3
-# unpack the tuple into three string and display them
+# Unpack the tuple into three strings and display them
 position1, position2, position3 = cardinal_numbers
 print(position1)
 print(position2)
@@ -23,7 +23,7 @@
 # Create a tuple containing the letters of your name from a string
 my_name = tuple("David")
 
-# Exercide 5
+# Exercise 5
 # Check whether or not x is in my_name
 print("x" in my_name)
 
diff --git a/ch09-lists-tuples-and-dictionaries/2-lists-are-mutable-sequences.py b/ch09-lists-tuples-and-dictionaries/2-lists-are-mutable-sequences.py
index 311fdb4..6151b2b 100644
--- a/ch09-lists-tuples-and-dictionaries/2-lists-are-mutable-sequences.py
+++ b/ch09-lists-tuples-and-dictionaries/2-lists-are-mutable-sequences.py
@@ -8,8 +8,8 @@
 
 
 # Exercise 2
-# Append the string "broccolo" to the food list using .append()
-food.append("brocolli")
+# Append the string "broccoli" to the food list using .append()
+food.append("broccoli")
 
 
 # Exercise 3
diff --git a/ch09-lists-tuples-and-dictionaries/3-nesting-sorting-and-copying-lists-and-tuples.py b/ch09-lists-tuples-and-dictionaries/3-nesting-sorting-and-copying-lists-and-tuples.py
index f9a3121..a7604b3 100644
--- a/ch09-lists-tuples-and-dictionaries/3-nesting-sorting-and-copying-lists-and-tuples.py
+++ b/ch09-lists-tuples-and-dictionaries/3-nesting-sorting-and-copying-lists-and-tuples.py
@@ -8,9 +8,11 @@
 
 
 # Exercise 2
-# Loop over data a print the sum of each nested tuple
-for i in range(len(data)):
-    print(f"Row {i+1} sum: {data[i][0] + data[i][1]}")
+# Loop over data and print the sum of each nested tuple
+index = 1
+for row in data:
+    print(f"Row {index} sum: {sum(row)}")
+    index += 1
 
 
 # Exercise 3
diff --git a/ch09-lists-tuples-and-dictionaries/4-challenge-list-of-lists.py b/ch09-lists-tuples-and-dictionaries/4-challenge-list-of-lists.py
index 48f22dd..f723245 100644
--- a/ch09-lists-tuples-and-dictionaries/4-challenge-list-of-lists.py
+++ b/ch09-lists-tuples-and-dictionaries/4-challenge-list-of-lists.py
@@ -3,7 +3,6 @@
 
 
 def enrollment_stats(list_of_universities):
-
     # Variables
     total_students = []
     total_tuition = []
@@ -25,7 +24,7 @@ def mean(values):
 def median(values):
     """Return the median value of the list `values`"""
     values.sort()
-    # If the number of valus is odd,
+    # If the number of values is odd,
     # return the middle value of the list
     if len(values) % 2 == 1:
         # The value at the center of the list is the value
@@ -36,8 +35,8 @@ def median(values):
     # Otherwise, if the length of the list is even, return
     # the mean of the two center values
     else:
-        left_center_index = (len(values) - 1) / 2
-        right_center_index = (len(values) + 1) / 2
+        left_center_index = (len(values) - 1) // 2
+        right_center_index = (len(values) + 1) // 2
         return mean([values[left_center_index], values[right_center_index]])
 
 
diff --git a/ch09-lists-tuples-and-dictionaries/5-challenge-wax-poetic.py b/ch09-lists-tuples-and-dictionaries/5-challenge-wax-poetic.py
index b6384a8..7b9ed8a 100644
--- a/ch09-lists-tuples-and-dictionaries/5-challenge-wax-poetic.py
+++ b/ch09-lists-tuples-and-dictionaries/5-challenge-wax-poetic.py
@@ -4,7 +4,7 @@
 
 # Generate a random poem based on a set structure
 
-from random import choice
+import random
 
 noun = [
     "fossil",
@@ -57,54 +57,57 @@
 def make_poem():
     """Create a randomly generated poem, returned as a multi-line string."""
     # Pull three nouns randomly
-    n1 = choice(noun)
-    n2 = choice(noun)
-    n3 = choice(noun)
+    n1 = random.choice(noun)
+    n2 = random.choice(noun)
+    n3 = random.choice(noun)
     # Make sure that all the nouns are different
     while n1 == n2:
-        n2 = choice(noun)
+        n2 = random.choice(noun)
     while n1 == n3 or n2 == n3:
-        n3 = choice(noun)
+        n3 = random.choice(noun)
 
     # Pull three different verbs
-    v1 = choice(verb)
-    v2 = choice(verb)
-    v3 = choice(verb)
+    v1 = random.choice(verb)
+    v2 = random.choice(verb)
+    v3 = random.choice(verb)
     while v1 == v2:
-        v2 = choice(verb)
+        v2 = random.choice(verb)
     while v1 == v3 or v2 == v3:
-        v3 = choice(verb)
+        v3 = random.choice(verb)
 
     # Pull three different adjectives
-    adj1 = choice(adjective)
-    adj2 = choice(adjective)
-    adj3 = choice(adjective)
+    adj1 = random.choice(adjective)
+    adj2 = random.choice(adjective)
+    adj3 = random.choice(adjective)
     while adj1 == adj2:
-        adj2 = choice(adjective)
+        adj2 = random.choice(adjective)
     while adj1 == adj3 or adj2 == adj3:
-        adj3 = choice(adjective)
+        adj3 = random.choice(adjective)
 
     # Pull two different prepositions
-    prep1 = choice(preposition)
-    prep2 = choice(preposition)
+    prep1 = random.choice(preposition)
+    prep2 = random.choice(preposition)
     while prep1 == prep2:
-        prep2 = choice(preposition)
+        prep2 = random.choice(preposition)
 
     # Pull one adverb
-    adv1 = choice(adverb)
+    adv1 = random.choice(adverb)
 
-    if "aeiou".find(adj1[0]) != -1:  # first letter is a vowel
+    if "aeiou".find(adj1[0]) != -1:  # First letter is a vowel
         article = "An"
     else:
         article = "A"
 
-    # add lines to poem
-    poem = f"{article} {adj1} {n1}\n\n"
-    poem = poem + f"{article} {adj1} {n1} {v1} {prep1} the {adj2} {n2}\n"
-    poem = poem + f"{adv1}, the {n1} {v2}\n"
-    poem = poem + f"the {n2} {v3} {prep2} a {adj3} {n3}"
+    # Create the poem
+    poem = (
+        f"{article} {adj1} {n1}\n\n"
+        f"{article} {adj1} {n1} {v1} {prep1} the {adj2} {n2}\n"
+        f"{adv1}, the {n1} {v2}\n"
+        f"the {n2} {v3} {prep2} a {adj3} {n3}"
+    )
 
     return poem
 
 
-print(make_poem())
+poem = make_poem()
+print(poem)
diff --git a/ch09-lists-tuples-and-dictionaries/6-store-relationships-in-dictionaries.py b/ch09-lists-tuples-and-dictionaries/6-store-relationships-in-dictionaries.py
index 89002d9..2d4509e 100644
--- a/ch09-lists-tuples-and-dictionaries/6-store-relationships-in-dictionaries.py
+++ b/ch09-lists-tuples-and-dictionaries/6-store-relationships-in-dictionaries.py
@@ -22,7 +22,7 @@
     captains["Discovery"] = "unknown"
 
 # Bonus points: you could instead loop over a list of names to check
-# for name in ["Enterprise", "Discovery"]:
+# for ship in ["Enterprise", "Discovery"]:
 #    if not ship in captains:
 #        captains[ship] = "unknown"
 
diff --git a/ch09-lists-tuples-and-dictionaries/7-challenge-capital-city-loop.py b/ch09-lists-tuples-and-dictionaries/7-challenge-capital-city-loop.py
index d662974..8eca70b 100644
--- a/ch09-lists-tuples-and-dictionaries/7-challenge-capital-city-loop.py
+++ b/ch09-lists-tuples-and-dictionaries/7-challenge-capital-city-loop.py
@@ -56,8 +56,11 @@
     "Wyoming": "Cheyenne",
 }
 
+# Pull random state and capital pair from the dict by casting to list of tuples
 state, capital = random.choice(list(capitals_dict.items()))
 
+# Game loop continues until the user inputs "exit"
+# or guesses the correct capital
 while True:
     guess = input(f"What is the capital of '{state}'? ").lower()
     if guess == "exit":
diff --git a/ch09-lists-tuples-and-dictionaries/9a-challenge-cats-with-hats.py b/ch09-lists-tuples-and-dictionaries/9a-challenge-cats-with-hats.py
index 3e081c0..74cb1ed 100644
--- a/ch09-lists-tuples-and-dictionaries/9a-challenge-cats-with-hats.py
+++ b/ch09-lists-tuples-and-dictionaries/9a-challenge-cats-with-hats.py
@@ -4,18 +4,30 @@
 
 def get_cats_with_hats(array_of_cats):
     cats_with_hats_on = []
+    # We want to walk around the circle 100 times
     for num in range(1, 100 + 1):
+        # Each time we walk around, we visit 100 cats
         for cat in range(1, 100 + 1):
+            # Determine whether to visit the cat
+            # Use modulo operator to visit every 2nd, 3rd, 4th,... etc.
             if cat % num == 0:
+                # Remove or add hat depending on
+                # whether the cat already has one
                 if array_of_cats[cat] is True:
                     array_of_cats[cat] = False
                 else:
                     array_of_cats[cat] = True
+
+    # Add all number of each cat with a hat to list
     for cat in range(1, 100 + 1):
-        if cats[cat] is True:
+        if array_of_cats[cat] is True:
             cats_with_hats_on.append(cat)
+
+    # Return the resulting list
     return cats_with_hats_on
 
 
+# Cats contains whether each cat already has a hat on,
+# by default all are set to false since none have been visited
 cats = [False] * (100 + 1)
 print(get_cats_with_hats(cats))
diff --git a/ch09-lists-tuples-and-dictionaries/9c-challenge-cats-with-hats.py b/ch09-lists-tuples-and-dictionaries/9c-challenge-cats-with-hats.py
index c154a31..1e4c885 100644
--- a/ch09-lists-tuples-and-dictionaries/9c-challenge-cats-with-hats.py
+++ b/ch09-lists-tuples-and-dictionaries/9c-challenge-cats-with-hats.py
@@ -4,17 +4,24 @@
 
 theCats = {}
 
+# By default, no cats have been visited
+# so we set every cat's number to False
 for i in range(1, 101):
     theCats[i] = False
 
+# Walk around the circle 100 times
 for i in range(1, 101):
+    # Visit all cats each time we do a lap
     for cats, hats in theCats.items():
+        # Determine whether or not we visit a cat
         if cats % i == 0:
+            # Add or remove the hat
             if theCats[cats]:
                 theCats[cats] = False
             else:
                 theCats[cats] = True
 
+# Print whether each cat has a hat
 for cats, hats in theCats.items():
     if theCats[cats]:
         print(f"Cat {cats} has a hat.")
diff --git a/ch10-primer-on-oop/3-inherit-from-other-classes.py b/ch10-primer-on-oop/3-inherit-from-other-classes.py
index fc9a395..36efe49 100644
--- a/ch10-primer-on-oop/3-inherit-from-other-classes.py
+++ b/ch10-primer-on-oop/3-inherit-from-other-classes.py
@@ -39,5 +39,9 @@ class Square(Rectangle):
     def __init__(self, side_length):
         super().__init__(side_length, side_length)
 
+
 square = Square(4)
-print(square.area())
+print(square.area())  # 16
+
+square.width = 5  # Modifies .width but not .length
+print(square.area())  # 20
diff --git a/ch11-modules-and-packages/1-working-with-modules/greeter.py b/ch11-modules-and-packages/1-working-with-modules/greeter.py
new file mode 100644
index 0000000..436349b
--- /dev/null
+++ b/ch11-modules-and-packages/1-working-with-modules/greeter.py
@@ -0,0 +1,6 @@
+# Ch 11.1 - Modules and Packages
+# Solution to Exercise 1
+
+
+def greet(name):
+    print(f"Hello {name}!")
diff --git a/ch11-modules-and-packages/1-working-with-modules/main.py b/ch11-modules-and-packages/1-working-with-modules/main.py
new file mode 100644
index 0000000..13cc631
--- /dev/null
+++ b/ch11-modules-and-packages/1-working-with-modules/main.py
@@ -0,0 +1,7 @@
+# Ch 11.1 - Modules and Packages
+# Solution to Exercise 2
+
+import greeter
+
+
+greeter.greet("Real Python")
diff --git a/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/__init__.py b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/__init__.py
new file mode 100644
index 0000000..6ea23c6
--- /dev/null
+++ b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/__init__.py
@@ -0,0 +1,2 @@
+# Ch 11.2 - Working With Packages
+# __init__.py - Part of solution to Exercise 1
diff --git a/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/math.py b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/math.py
new file mode 100644
index 0000000..745c003
--- /dev/null
+++ b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/math.py
@@ -0,0 +1,6 @@
+# Ch 11.2 - Working With Packages
+# helpers/math.py - Part of solution to Exercise 1
+
+
+def area(length, width):
+    return length * width
diff --git a/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/string.py b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/string.py
new file mode 100644
index 0000000..a6480aa
--- /dev/null
+++ b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/helpers/string.py
@@ -0,0 +1,6 @@
+# Ch 11.2 - Working With Packages
+# helpers/string.py - Part of solution to Exercise 1
+
+
+def shout(string):
+    return string.upper()
diff --git a/ch11-modules-and-packages/2-working-with-packages/packages_exercises/main.py b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/main.py
new file mode 100644
index 0000000..33c8648
--- /dev/null
+++ b/ch11-modules-and-packages/2-working-with-packages/packages_exercises/main.py
@@ -0,0 +1,11 @@
+# Ch 11.2 - Working With Packages
+# main.py - Solution to Exercise 2
+
+from helpers.string import shout
+from helpers.math import area
+
+
+length = 5
+width = 8
+message = f"The area of a {length}-by-{width} rectangle is {area(length, width)}"
+print(shout(message))
diff --git a/ch11-file-input-and-output/2-working-with-file-paths-in-python.py b/ch12-file-input-and-output/2-working-with-file-paths-in-python.py
similarity index 85%
rename from ch11-file-input-and-output/2-working-with-file-paths-in-python.py
rename to ch12-file-input-and-output/2-working-with-file-paths-in-python.py
index 86e2a21..8726232 100644
--- a/ch11-file-input-and-output/2-working-with-file-paths-in-python.py
+++ b/ch12-file-input-and-output/2-working-with-file-paths-in-python.py
@@ -1,4 +1,4 @@
-# 11.2 - Working With File Paths in Python
+# 12.2 - Working With File Paths in Python
 # Solutions to review exercises
 
 
diff --git a/ch11-file-input-and-output/3-common-file-system-operations.py b/ch12-file-input-and-output/3-common-file-system-operations.py
similarity index 89%
rename from ch11-file-input-and-output/3-common-file-system-operations.py
rename to ch12-file-input-and-output/3-common-file-system-operations.py
index 2633350..eaf8042 100644
--- a/ch11-file-input-and-output/3-common-file-system-operations.py
+++ b/ch12-file-input-and-output/3-common-file-system-operations.py
@@ -1,4 +1,4 @@
-# 11.3 Common File System Operations
+# 12.3 Common File System Operations
 # Solutions to Exercises
 
 
@@ -29,6 +29,7 @@
 file1.unlink()
 
 
-# # Exercise 5
+# Exercise 5
 import shutil
+
 shutil.rmtree(new_dir)
diff --git a/ch11-file-input-and-output/4-challenge-move-all-image-files-to-a-new-directory.py b/ch12-file-input-and-output/4-challenge-move-all-image-files-to-a-new-directory.py
similarity index 69%
rename from ch11-file-input-and-output/4-challenge-move-all-image-files-to-a-new-directory.py
rename to ch12-file-input-and-output/4-challenge-move-all-image-files-to-a-new-directory.py
index 82ea7b4..b39266c 100644
--- a/ch11-file-input-and-output/4-challenge-move-all-image-files-to-a-new-directory.py
+++ b/ch12-file-input-and-output/4-challenge-move-all-image-files-to-a-new-directory.py
@@ -1,16 +1,10 @@
-# 11.4 Challenge: Move All Image Files To a New Directory
+# 12.4 Challenge: Move All Image Files To a New Directory
 # Solution to Challenge
 
 from pathlib import Path
 
 # Change this path to match the location on your computer
-documents_dir = (
-    Path.home() /
-    "python-basics-exercises" /
-    "ch11-file-input-and-output" /
-    "practice_files" /
-    "documents"
-)
+documents_dir = Path.cwd() / "practice_files" / "documents"
 
 # Create an images/ directory in your home directory
 images_dir = Path.home() / "images"
diff --git a/ch11-file-input-and-output/5-reading-and-writing-files.py b/ch12-file-input-and-output/5-reading-and-writing-files.py
similarity index 94%
rename from ch11-file-input-and-output/5-reading-and-writing-files.py
rename to ch12-file-input-and-output/5-reading-and-writing-files.py
index 498791a..2dd4f0c 100644
--- a/ch11-file-input-and-output/5-reading-and-writing-files.py
+++ b/ch12-file-input-and-output/5-reading-and-writing-files.py
@@ -1,4 +1,4 @@
-# 11.5 - Reading and Writing Files
+# 12.5 - Reading and Writing Files
 # Solutions to Exercises
 
 
diff --git a/ch11-file-input-and-output/6-read-and-write-csv-data.py b/ch12-file-input-and-output/6-read-and-write-csv-data.py
similarity index 97%
rename from ch11-file-input-and-output/6-read-and-write-csv-data.py
rename to ch12-file-input-and-output/6-read-and-write-csv-data.py
index 5114e2f..233b1d4 100644
--- a/ch11-file-input-and-output/6-read-and-write-csv-data.py
+++ b/ch12-file-input-and-output/6-read-and-write-csv-data.py
@@ -1,4 +1,4 @@
-# 11.5 Read and Write CSV Data
+# 12.5 Read and Write CSV Data
 # Solutions to Exercises
 
 
diff --git a/ch11-file-input-and-output/7-challenge-create-a-high-scores-list.py b/ch12-file-input-and-output/7-challenge-create-a-high-scores-list.py
similarity index 81%
rename from ch11-file-input-and-output/7-challenge-create-a-high-scores-list.py
rename to ch12-file-input-and-output/7-challenge-create-a-high-scores-list.py
index ee8a9a1..f9539f8 100644
--- a/ch11-file-input-and-output/7-challenge-create-a-high-scores-list.py
+++ b/ch12-file-input-and-output/7-challenge-create-a-high-scores-list.py
@@ -1,4 +1,4 @@
-# 11.7 Challenge: Create a High Scores List
+# 12.7 Challenge: Create a High Scores List
 # Solution to Challenge
 
 import csv
@@ -6,12 +6,9 @@
 
 # Change the path below to match the location on your computer
 scores_csv_path = (
-    Path.home() /
-    "github/realpython" /
-    "python-basics-exercises" /
-    "ch11-file-input-and-output" /
-    "practice_files" /
-    "scores.csv"
+    Path.cwd()
+    / "practice_files"
+    / "scores.csv"
 )
 
 with scores_csv_path.open(mode="r", encoding="utf-8") as file:
@@ -21,7 +18,7 @@
 high_scores = {}
 for item in scores:
     name = item["name"]
-    score = item["score"]
+    score = int(item["score"])
     # If the name has not been added to the high_score dictionary, then
     # create a new key with the name and set its value to the score
     if name not in high_scores:
@@ -35,9 +32,10 @@
 # The high_scores dictionary now contains one key for each name that was
 # in the scores.csv file, and each value is that player's highest score.
 
-output_csv_file = Path.home() / "high_scores.csv"
+output_csv_file = Path.cwd() / "high_scores.csv"
 with output_csv_file.open(mode="w", encoding="utf-8") as file:
     writer = csv.DictWriter(file, fieldnames=["name", "high_score"])
+    writer.writeheader()
     for name in high_scores:
         row_dict = {"name": name, "high_score": high_scores[name]}
         writer.writerow(row_dict)
diff --git a/ch11-file-input-and-output/practice_files/documents/files/additional files/image3.png b/ch12-file-input-and-output/practice_files/documents/files/additional files/image3.png
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/files/additional files/image3.png
rename to ch12-file-input-and-output/practice_files/documents/files/additional files/image3.png
diff --git a/ch11-file-input-and-output/practice_files/documents/files/dad.txt b/ch12-file-input-and-output/practice_files/documents/files/dad.txt
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/files/dad.txt
rename to ch12-file-input-and-output/practice_files/documents/files/dad.txt
diff --git a/ch11-file-input-and-output/practice_files/documents/files/stuff.csv b/ch12-file-input-and-output/practice_files/documents/files/stuff.csv
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/files/stuff.csv
rename to ch12-file-input-and-output/practice_files/documents/files/stuff.csv
diff --git a/ch11-file-input-and-output/practice_files/documents/image1.png b/ch12-file-input-and-output/practice_files/documents/image1.png
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/image1.png
rename to ch12-file-input-and-output/practice_files/documents/image1.png
diff --git a/ch11-file-input-and-output/practice_files/documents/more_files/even_more_files/image4.jpg b/ch12-file-input-and-output/practice_files/documents/more_files/even_more_files/image4.jpg
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/more_files/even_more_files/image4.jpg
rename to ch12-file-input-and-output/practice_files/documents/more_files/even_more_files/image4.jpg
diff --git a/ch11-file-input-and-output/practice_files/documents/more_files/even_more_files/the_answer.txt b/ch12-file-input-and-output/practice_files/documents/more_files/even_more_files/the_answer.txt
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/more_files/even_more_files/the_answer.txt
rename to ch12-file-input-and-output/practice_files/documents/more_files/even_more_files/the_answer.txt
diff --git a/ch11-file-input-and-output/practice_files/documents/more_files/image2.gif b/ch12-file-input-and-output/practice_files/documents/more_files/image2.gif
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/more_files/image2.gif
rename to ch12-file-input-and-output/practice_files/documents/more_files/image2.gif
diff --git a/ch11-file-input-and-output/practice_files/documents/more_files/mom.txt b/ch12-file-input-and-output/practice_files/documents/more_files/mom.txt
similarity index 100%
rename from ch11-file-input-and-output/practice_files/documents/more_files/mom.txt
rename to ch12-file-input-and-output/practice_files/documents/more_files/mom.txt
diff --git a/ch11-file-input-and-output/practice_files/scores.csv b/ch12-file-input-and-output/practice_files/scores.csv
similarity index 100%
rename from ch11-file-input-and-output/practice_files/scores.csv
rename to ch12-file-input-and-output/practice_files/scores.csv
diff --git a/ch13-interact-with-pdf-files/1-extract-text-from-a-pdf.py b/ch14-interact-with-pdf-files/1-extract-text-from-a-pdf.py
similarity index 87%
rename from ch13-interact-with-pdf-files/1-extract-text-from-a-pdf.py
rename to ch14-interact-with-pdf-files/1-extract-text-from-a-pdf.py
index 1c44e4e..49e1d76 100644
--- a/ch13-interact-with-pdf-files/1-extract-text-from-a-pdf.py
+++ b/ch14-interact-with-pdf-files/1-extract-text-from-a-pdf.py
@@ -1,4 +1,4 @@
-# 13.1 - Extract Text From a PDF
+# 14.1 - Extract Text From a PDF
 # Solutions to review exercises
 
 
@@ -15,11 +15,10 @@
 from PyPDF2 import PdfFileReader
 
 # To create a PdfFileReader instance, you need to path to the PDF file.
-# We'll assume you downloaded the solutions folder and extracted it into
-# the home directory on your computer. If this is not the case, you'll
+# We'll assume you downloaded the solutions folder and are running this
+# program from the solutions folder. If this is not the case, you'll
 # need to update the path below.
-pdf_path = Path.home() / "python-basics-exercises/ch13-interact-with-pdf-files" \
-    "/practice_files/zen.pdf"
+pdf_path = Path.cwd() / "practice_files" / "zen.pdf"
 
 # Now you can create the PdfFileReader instance. Remember that
 # PdfFileReader objects can only be instantiated with path strings, not
diff --git a/ch13-interact-with-pdf-files/2-extract-pages-from-a-pdf.py b/ch14-interact-with-pdf-files/2-extract-pages-from-a-pdf.py
similarity index 96%
rename from ch13-interact-with-pdf-files/2-extract-pages-from-a-pdf.py
rename to ch14-interact-with-pdf-files/2-extract-pages-from-a-pdf.py
index b0946cb..fc34b2b 100644
--- a/ch13-interact-with-pdf-files/2-extract-pages-from-a-pdf.py
+++ b/ch14-interact-with-pdf-files/2-extract-pages-from-a-pdf.py
@@ -1,4 +1,4 @@
-# 13.2 - Extract Pages From a PDF
+# 14.2 - Extract Pages From a PDF
 # Solutions to review exercises
 
 # ***********
@@ -16,8 +16,7 @@
 # downloaded the solutions folder and extracted it into the home
 # directory on your computer. If this is not the case, you'll need to
 # update the path below.
-pdf_path = Path.home() / "python-basics-exercises/ch13-interact-with-pdf-files" \
-    "/practice_files/Pride_and_Prejudice.pdf"
+pdf_path = Path.home() / "python-basics-exercises/ch14-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf"
 
 # Now you can create the PdfFileReader instance. Remember that
 # PdfFileReader objects can only be instantiated with path strings, not
diff --git a/ch13-interact-with-pdf-files/3-challenge-PdfFileSplitter-class.py b/ch14-interact-with-pdf-files/3-challenge-PdfFileSplitter-class.py
similarity index 94%
rename from ch13-interact-with-pdf-files/3-challenge-PdfFileSplitter-class.py
rename to ch14-interact-with-pdf-files/3-challenge-PdfFileSplitter-class.py
index 4d2cabb..5357574 100644
--- a/ch13-interact-with-pdf-files/3-challenge-PdfFileSplitter-class.py
+++ b/ch14-interact-with-pdf-files/3-challenge-PdfFileSplitter-class.py
@@ -1,4 +1,4 @@
-# 13.5 - Challenge: PdfFileSplitter Class
+# 14.5 - Challenge: PdfFileSplitter Class
 # Solution to challenge
 
 from pathlib import Path
@@ -42,6 +42,6 @@ def write(self, filename):
 # Split the Pride_and_Prejudice.pdf file into two PDFs, the first
 # containing the first 150 pages, and the second containing the
 # remaining pages.
-pdf_splitter = PdfFileSplitter("ch13-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf")
+pdf_splitter = PdfFileSplitter("ch14-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf")
 pdf_splitter.split(breakpoint=150)
 pdf_splitter.write("pride_split")
diff --git a/ch13-interact-with-pdf-files/4-concatenating-and-merging-pdfs.py b/ch14-interact-with-pdf-files/4-concatenating-and-merging-pdfs.py
similarity index 89%
rename from ch13-interact-with-pdf-files/4-concatenating-and-merging-pdfs.py
rename to ch14-interact-with-pdf-files/4-concatenating-and-merging-pdfs.py
index e82f700..0753bf6 100644
--- a/ch13-interact-with-pdf-files/4-concatenating-and-merging-pdfs.py
+++ b/ch14-interact-with-pdf-files/4-concatenating-and-merging-pdfs.py
@@ -1,4 +1,4 @@
-# 13.4 - Concatenating and Merging PDFs
+# 14.4 - Concatenating and Merging PDFs
 # Solutions to review exercises
 
 # ***********
@@ -15,8 +15,7 @@
 from PyPDF2 import PdfFileMerger
 
 
-BASE_PATH = Path.home() / "python-basics-exercises/" \
-    "ch13-interact-with-pdf-files/practice_files"
+BASE_PATH = Path.cwd() / "practice_files"
 
 pdf_paths = [BASE_PATH / "merge1.pdf", BASE_PATH / "merge2.pdf"]
 pdf_merger = PdfFileMerger()
diff --git a/ch13-interact-with-pdf-files/5-rotating-and-cropping-pdf-pages.py b/ch14-interact-with-pdf-files/5-rotating-and-cropping-pdf-pages.py
similarity index 92%
rename from ch13-interact-with-pdf-files/5-rotating-and-cropping-pdf-pages.py
rename to ch14-interact-with-pdf-files/5-rotating-and-cropping-pdf-pages.py
index 5a52d89..3abe217 100644
--- a/ch13-interact-with-pdf-files/5-rotating-and-cropping-pdf-pages.py
+++ b/ch14-interact-with-pdf-files/5-rotating-and-cropping-pdf-pages.py
@@ -1,4 +1,4 @@
-# 13.5 - Rotating and Cropping PDF pages
+# 14.5 - Rotating and Cropping PDF pages
 # Solutions to review exercises
 
 # ***********
@@ -15,8 +15,7 @@
 from PyPDF2 import PdfFileReader, PdfFileWriter
 
 
-pdf_path = Path.home() / "python-basics-exercises/" \
-    "ch13-interact-with-pdf-files/practice_files/split_and_rotate.pdf"
+pdf_path = Path.cwd() / "practice_files" / "split_and_rotate.pdf"
 
 pdf_reader = PdfFileReader(str(pdf_path))
 pdf_writer = PdfFileWriter()
diff --git a/ch13-interact-with-pdf-files/6-encrypting-and-decrypting-pdfs.py b/ch14-interact-with-pdf-files/6-encrypting-and-decrypting-pdfs.py
similarity index 86%
rename from ch13-interact-with-pdf-files/6-encrypting-and-decrypting-pdfs.py
rename to ch14-interact-with-pdf-files/6-encrypting-and-decrypting-pdfs.py
index 889110d..22a365a 100644
--- a/ch13-interact-with-pdf-files/6-encrypting-and-decrypting-pdfs.py
+++ b/ch14-interact-with-pdf-files/6-encrypting-and-decrypting-pdfs.py
@@ -1,4 +1,4 @@
-# 13.6 - Encrypting and Decrypting PDFs
+# 14.6 - Encrypting and Decrypting PDFs
 # Solutions to review exercises
 
 # ***********
@@ -15,8 +15,7 @@
 from PyPDF2 import PdfFileReader, PdfFileWriter
 
 
-pdf_path = Path.home() / "python-basics-exercises/" \
-    "ch13-interact-with-pdf-files/practice_files/top_secret.pdf"
+pdf_path = Path.cwd() / "practice_files" / "top_secret.pdf"
 
 pdf_reader = PdfFileReader(str(pdf_path))
 pdf_writer = PdfFileWriter()
diff --git a/ch13-interact-with-pdf-files/7-challenge-unscramble-a-pdf.py b/ch14-interact-with-pdf-files/7-challenge-unscramble-a-pdf.py
similarity index 77%
rename from ch13-interact-with-pdf-files/7-challenge-unscramble-a-pdf.py
rename to ch14-interact-with-pdf-files/7-challenge-unscramble-a-pdf.py
index 492d9ea..ded54b2 100644
--- a/ch13-interact-with-pdf-files/7-challenge-unscramble-a-pdf.py
+++ b/ch14-interact-with-pdf-files/7-challenge-unscramble-a-pdf.py
@@ -1,4 +1,4 @@
-# 13.7 - Challenge: Unscramble a PDF
+# 14.7 - Challenge: Unscramble a PDF
 # Solution to challenge
 
 from pathlib import Path
@@ -10,8 +10,7 @@ def get_page_text(page):
     return page.extractText()
 
 
-pdf_path = Path.home() / "github/realpython/python-basics-exercises/" \
-    "ch13-interact-with-pdf-files/practice_files/scrambled.pdf"
+pdf_path = Path.cwd() / "practice_files" / "scrambled.pdf"
 
 pdf_reader = PdfFileReader(str(pdf_path))
 pdf_writer = PdfFileWriter()
diff --git a/ch13-interact-with-pdf-files/practice_files/Emperor cover sheet.pdf b/ch14-interact-with-pdf-files/practice_files/Emperor cover sheet.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/Emperor cover sheet.pdf
rename to ch14-interact-with-pdf-files/practice_files/Emperor cover sheet.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf b/ch14-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf
rename to ch14-interact-with-pdf-files/practice_files/Pride_and_Prejudice.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/The Emperor.pdf b/ch14-interact-with-pdf-files/practice_files/The Emperor.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/The Emperor.pdf
rename to ch14-interact-with-pdf-files/practice_files/The Emperor.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/expense_reports/Expense report 1.pdf b/ch14-interact-with-pdf-files/practice_files/expense_reports/Expense report 1.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/expense_reports/Expense report 1.pdf
rename to ch14-interact-with-pdf-files/practice_files/expense_reports/Expense report 1.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/expense_reports/Expense report 2.pdf b/ch14-interact-with-pdf-files/practice_files/expense_reports/Expense report 2.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/expense_reports/Expense report 2.pdf
rename to ch14-interact-with-pdf-files/practice_files/expense_reports/Expense report 2.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/expense_reports/Expense report 3.pdf b/ch14-interact-with-pdf-files/practice_files/expense_reports/Expense report 3.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/expense_reports/Expense report 3.pdf
rename to ch14-interact-with-pdf-files/practice_files/expense_reports/Expense report 3.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/half_and_half.pdf b/ch14-interact-with-pdf-files/practice_files/half_and_half.pdf
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rename from ch13-interact-with-pdf-files/practice_files/half_and_half.pdf
rename to ch14-interact-with-pdf-files/practice_files/half_and_half.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/merge1.pdf b/ch14-interact-with-pdf-files/practice_files/merge1.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/merge1.pdf
rename to ch14-interact-with-pdf-files/practice_files/merge1.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/merge2.pdf b/ch14-interact-with-pdf-files/practice_files/merge2.pdf
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rename from ch13-interact-with-pdf-files/practice_files/merge2.pdf
rename to ch14-interact-with-pdf-files/practice_files/merge2.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/merge3.pdf b/ch14-interact-with-pdf-files/practice_files/merge3.pdf
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rename from ch13-interact-with-pdf-files/practice_files/merge3.pdf
rename to ch14-interact-with-pdf-files/practice_files/merge3.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/newsletter.pdf b/ch14-interact-with-pdf-files/practice_files/newsletter.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/newsletter.pdf
rename to ch14-interact-with-pdf-files/practice_files/newsletter.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/quarterly_report/full_report.pdf b/ch14-interact-with-pdf-files/practice_files/quarterly_report/full_report.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/quarterly_report/full_report.pdf
rename to ch14-interact-with-pdf-files/practice_files/quarterly_report/full_report.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/quarterly_report/report.pdf b/ch14-interact-with-pdf-files/practice_files/quarterly_report/report.pdf
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rename from ch13-interact-with-pdf-files/practice_files/quarterly_report/report.pdf
rename to ch14-interact-with-pdf-files/practice_files/quarterly_report/report.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/quarterly_report/toc.pdf b/ch14-interact-with-pdf-files/practice_files/quarterly_report/toc.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/quarterly_report/toc.pdf
rename to ch14-interact-with-pdf-files/practice_files/quarterly_report/toc.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/scrambled.pdf b/ch14-interact-with-pdf-files/practice_files/scrambled.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/scrambled.pdf
rename to ch14-interact-with-pdf-files/practice_files/scrambled.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/split_and_rotate.pdf b/ch14-interact-with-pdf-files/practice_files/split_and_rotate.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/split_and_rotate.pdf
rename to ch14-interact-with-pdf-files/practice_files/split_and_rotate.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/top_secret.pdf b/ch14-interact-with-pdf-files/practice_files/top_secret.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/top_secret.pdf
rename to ch14-interact-with-pdf-files/practice_files/top_secret.pdf
diff --git a/ch13-interact-with-pdf-files/practice_files/ugly.pdf b/ch14-interact-with-pdf-files/practice_files/ugly.pdf
similarity index 100%
rename from ch13-interact-with-pdf-files/practice_files/ugly.pdf
rename to ch14-interact-with-pdf-files/practice_files/ugly.pdf
diff --git a/ch14-interact-with-pdf-files/practice_files/zen.pdf b/ch14-interact-with-pdf-files/practice_files/zen.pdf
new file mode 100644
index 0000000..839484f
Binary files /dev/null and b/ch14-interact-with-pdf-files/practice_files/zen.pdf differ
diff --git a/ch14-sql-database-connections/1-use-sqlite.py b/ch14-sql-database-connections/1-use-sqlite.py
deleted file mode 100644
index 483d0e9..0000000
--- a/ch14-sql-database-connections/1-use-sqlite.py
+++ /dev/null
@@ -1,33 +0,0 @@
-# 14.1 - Use SQLite
-# Solutions to review exercises
-
-import sqlite3
-
-# Create a temporary database connection in RAM
-with sqlite3.connect(":memory:") as connection:
-    c = connection.cursor()
-
-    # Exercise 1
-    # Create a "Roster" table with Name, Species and IQ fields
-    c.execute("CREATE TABLE Roster(Name TEXT, Species TEXT, IQ INT)")
-
-    # Exercise 2
-    # Add some data into the database
-    roster_data = (
-        ("Jean-Baptiste Zorg", "Human", 122),
-        ("Korben Dallas", "Meat Popsicle", 100),
-        ("Ak'not", "Mangalore", -5),
-    )
-    c.executemany("INSERT INTO Roster VALUES(?, ?, ?)", roster_data)
-
-    # Exercise 3
-    # Update the Species of Korben Dallas to "Human"
-    c.execute(
-        "UPDATE Roster SET Species=? WHERE Name=?", ("Human", "Korben Dallas")
-    )
-
-    # Exercise 4
-    # Display the names and IQs of everyone classified as Human
-    c.execute("SELECT Name, IQ FROM Roster WHERE Species = 'Human'")
-    for row in c.fetchall():
-        print(row)
diff --git a/ch15-sql-database-connections/1-use-sqlite.py b/ch15-sql-database-connections/1-use-sqlite.py
new file mode 100644
index 0000000..d5cfc09
--- /dev/null
+++ b/ch15-sql-database-connections/1-use-sqlite.py
@@ -0,0 +1,33 @@
+# 15.1 - Use SQLite
+# Solutions to review exercises
+
+import sqlite3
+
+# Create a temporary database connection in RAM
+with sqlite3.connect(":memory:") as connection:
+    c = connection.cursor()
+
+    # Exercise 1
+    # Create a "Roster" table with Name, Species and Age fields
+    c.execute("CREATE TABLE Roster(Name TEXT, Species TEXT, Age INT)")
+
+    # Exercise 2
+    # Add some data into the database
+    roster_data = (
+        ("Benjamin Sisko", "Human", 40),
+        ("Jadzia Dax", "Trill", 300),
+        ("Kira Nerys", "Bajoran", 29),
+    )
+    c.executemany("INSERT INTO Roster VALUES(?, ?, ?)", roster_data)
+
+    # Exercise 3
+    # Update the Name of Jadzia Dax to "Ezri Dax"
+    c.execute(
+        "UPDATE Roster SET Name=? WHERE Name=?", ("Ezri Dax", "Jadzia Dax")
+    )
+
+    # Exercise 4
+    # Display the names and ages of everyone classified as Bajoran
+    c.execute("SELECT Name, Age FROM Roster WHERE Species = 'Bajoran'")
+    for row in c.fetchall():
+        print(row)
diff --git a/ch15-interacting-with-the-web/1-scrape-and-parse-text-from-websites.py b/ch16-interacting-with-the-web/1-scrape-and-parse-text-from-websites.py
similarity index 95%
rename from ch15-interacting-with-the-web/1-scrape-and-parse-text-from-websites.py
rename to ch16-interacting-with-the-web/1-scrape-and-parse-text-from-websites.py
index 7f33108..851515d 100644
--- a/ch15-interacting-with-the-web/1-scrape-and-parse-text-from-websites.py
+++ b/ch16-interacting-with-the-web/1-scrape-and-parse-text-from-websites.py
@@ -1,4 +1,4 @@
-# 15.1 - Scrape and Parse Text From Websites
+# 16.1 - Scrape and Parse Text From Websites
 # Solutions to review exercises
 
 from urllib.request import urlopen
diff --git a/ch15-interacting-with-the-web/2-use-an-html-parser-to-scrape-websites.py b/ch16-interacting-with-the-web/2-use-an-html-parser-to-scrape-websites.py
similarity index 95%
rename from ch15-interacting-with-the-web/2-use-an-html-parser-to-scrape-websites.py
rename to ch16-interacting-with-the-web/2-use-an-html-parser-to-scrape-websites.py
index 8b70919..4781c1f 100644
--- a/ch15-interacting-with-the-web/2-use-an-html-parser-to-scrape-websites.py
+++ b/ch16-interacting-with-the-web/2-use-an-html-parser-to-scrape-websites.py
@@ -1,4 +1,4 @@
-# 15.2 - Use an HTML Parser to Scrape Websites
+# 16.2 - Use an HTML Parser to Scrape Websites
 # Solutions to review exercises
 
 # Make sure BeautifulSoup is installed first with:
diff --git a/ch15-interacting-with-the-web/3-interact-with-html-forms.py b/ch16-interacting-with-the-web/3-interact-with-html-forms.py
similarity index 97%
rename from ch15-interacting-with-the-web/3-interact-with-html-forms.py
rename to ch16-interacting-with-the-web/3-interact-with-html-forms.py
index c1741e3..26eaf2a 100644
--- a/ch15-interacting-with-the-web/3-interact-with-html-forms.py
+++ b/ch16-interacting-with-the-web/3-interact-with-html-forms.py
@@ -1,4 +1,4 @@
-# 15.3 - Interact with HTML Forms
+# 16.3 - Interact with HTML Forms
 # Solutions to review exercises
 
 # Make sure BeautifulSoup is installed first with:
diff --git a/ch15-interacting-with-the-web/4-interact-with-websites-in-realtime.py b/ch16-interacting-with-the-web/4-interact-with-websites-in-realtime.py
similarity index 95%
rename from ch15-interacting-with-the-web/4-interact-with-websites-in-realtime.py
rename to ch16-interacting-with-the-web/4-interact-with-websites-in-realtime.py
index 60ac5ee..90767c1 100644
--- a/ch15-interacting-with-the-web/4-interact-with-websites-in-realtime.py
+++ b/ch16-interacting-with-the-web/4-interact-with-websites-in-realtime.py
@@ -1,4 +1,4 @@
-# 15.4 - Interact With Websites in Real-Time
+# 16.4 - Interact With Websites in Real-Time
 # Solutions to review exercise
 
 # Make sure BeautifulSoup is installed first with:
diff --git a/ch16-scientific-computing-and-graphing/1-use-numpy-for-matrix-manipulation.py b/ch17-scientific-computing-and-graphing/1-use-numpy-for-matrix-manipulation.py
similarity index 90%
rename from ch16-scientific-computing-and-graphing/1-use-numpy-for-matrix-manipulation.py
rename to ch17-scientific-computing-and-graphing/1-use-numpy-for-matrix-manipulation.py
index 839fc31..20a3307 100644
--- a/ch16-scientific-computing-and-graphing/1-use-numpy-for-matrix-manipulation.py
+++ b/ch17-scientific-computing-and-graphing/1-use-numpy-for-matrix-manipulation.py
@@ -1,4 +1,4 @@
-# 16.2 - Use matplotlib for Plotting Graphs
+# 17.2 - Use matplotlib for Plotting Graphs
 # Solution to review exercise #2
 
 # Setup
@@ -17,7 +17,7 @@
 
 # Exercise 3
 # Square every entry and save in a new matrix
-second_matrix = first_matrix ** 2
+second_matrix = first_matrix**2
 
 # Exercise 4
 # Put first_matrix on top of second_matrix
diff --git a/ch16-scientific-computing-and-graphing/2-use-matplotlib-for-plotting-graphs.py b/ch17-scientific-computing-and-graphing/2-use-matplotlib-for-plotting-graphs.py
similarity index 92%
rename from ch16-scientific-computing-and-graphing/2-use-matplotlib-for-plotting-graphs.py
rename to ch17-scientific-computing-and-graphing/2-use-matplotlib-for-plotting-graphs.py
index 92f778b..3afa8eb 100644
--- a/ch16-scientific-computing-and-graphing/2-use-matplotlib-for-plotting-graphs.py
+++ b/ch17-scientific-computing-and-graphing/2-use-matplotlib-for-plotting-graphs.py
@@ -1,4 +1,4 @@
-# 16.3 - Use matplotlib for Plotting Graphs
+# 17.3 - Use matplotlib for Plotting Graphs
 # Solution to review exercise #2
 
 # Graph pirates versus global warming
@@ -8,8 +8,7 @@
 import os
 
 # Change `path` to actual path on your system
-path = "C:/Real Python/python-basics-exercises/ch16-scientific-computing-and-graphing/\
-practice_files"
+path = "C:/Real Python/python-basics-exercises/ch16-scientific-computing-and-graphing/practice_files"
 
 years = []
 temperatures = []
diff --git a/ch16-scientific-computing-and-graphing/practice_files/pirates.csv b/ch17-scientific-computing-and-graphing/practice_files/pirates.csv
similarity index 100%
rename from ch16-scientific-computing-and-graphing/practice_files/pirates.csv
rename to ch17-scientific-computing-and-graphing/practice_files/pirates.csv
diff --git a/ch17-graphical-user-interfaces/1-add-gui-elements-with-easygui.py b/ch18-graphical-user-interfaces/1-add-gui-elements-with-easygui.py
similarity index 82%
rename from ch17-graphical-user-interfaces/1-add-gui-elements-with-easygui.py
rename to ch18-graphical-user-interfaces/1-add-gui-elements-with-easygui.py
index 3fe3780..bd09fb9 100644
--- a/ch17-graphical-user-interfaces/1-add-gui-elements-with-easygui.py
+++ b/ch18-graphical-user-interfaces/1-add-gui-elements-with-easygui.py
@@ -1,4 +1,4 @@
-# 17.1 - Add GUI Elements with EasyGUI
+# 18.1 - Add GUI Elements with EasyGUI
 # Review Exercises
 
 import easygui as gui
diff --git a/ch17-graphical-user-interfaces/10-challenge-return-of-the-poet.py b/ch18-graphical-user-interfaces/10-challenge-return-of-the-poet.py
similarity index 99%
rename from ch17-graphical-user-interfaces/10-challenge-return-of-the-poet.py
rename to ch18-graphical-user-interfaces/10-challenge-return-of-the-poet.py
index 5373168..b7af37f 100644
--- a/ch17-graphical-user-interfaces/10-challenge-return-of-the-poet.py
+++ b/ch18-graphical-user-interfaces/10-challenge-return-of-the-poet.py
@@ -1,4 +1,4 @@
-# 17.10 - Challenge: Return of the Poet
+# 18.10 - Challenge: Return of the Poet
 # Solution to challenge
 
 # Please note that there are many ways to solve this challenge. The code
diff --git a/ch17-graphical-user-interfaces/2-example-app-pdf-page-rotator.py b/ch18-graphical-user-interfaces/2-example-app-pdf-page-rotator.py
similarity index 98%
rename from ch17-graphical-user-interfaces/2-example-app-pdf-page-rotator.py
rename to ch18-graphical-user-interfaces/2-example-app-pdf-page-rotator.py
index ea097f6..3399e32 100644
--- a/ch17-graphical-user-interfaces/2-example-app-pdf-page-rotator.py
+++ b/ch18-graphical-user-interfaces/2-example-app-pdf-page-rotator.py
@@ -1,4 +1,4 @@
-# 17.2 - Example App: PDF Page Rotator
+# 18.2 - Example App: PDF Page Rotator
 # Review Exercise #1
 
 import easygui as gui
diff --git a/ch17-graphical-user-interfaces/3-challenge-use-gui-elements-to-help-a-user-modify-files.py b/ch18-graphical-user-interfaces/3-challenge-use-gui-elements-to-help-a-user-modify-files.py
similarity index 98%
rename from ch17-graphical-user-interfaces/3-challenge-use-gui-elements-to-help-a-user-modify-files.py
rename to ch18-graphical-user-interfaces/3-challenge-use-gui-elements-to-help-a-user-modify-files.py
index 0a76cfc..128dd6a 100644
--- a/ch17-graphical-user-interfaces/3-challenge-use-gui-elements-to-help-a-user-modify-files.py
+++ b/ch18-graphical-user-interfaces/3-challenge-use-gui-elements-to-help-a-user-modify-files.py
@@ -1,4 +1,4 @@
-# 17.3 - Challenge: Use GUI Elements to Help a User Modify Files
+# 18.3 - Challenge: Use GUI Elements to Help a User Modify Files
 # Solution to challenge
 
 # save part of a PDF based on a user-supplied page range using a GUI
diff --git a/ch17-graphical-user-interfaces/4-introduction-to-tkinter.py b/ch18-graphical-user-interfaces/4-introduction-to-tkinter.py
similarity index 91%
rename from ch17-graphical-user-interfaces/4-introduction-to-tkinter.py
rename to ch18-graphical-user-interfaces/4-introduction-to-tkinter.py
index 3027770..8f612c8 100644
--- a/ch17-graphical-user-interfaces/4-introduction-to-tkinter.py
+++ b/ch18-graphical-user-interfaces/4-introduction-to-tkinter.py
@@ -1,4 +1,4 @@
-# 17.4 - Introduction to Tkinter
+# 18.4 - Introduction to Tkinter
 # Review exercises
 
 import tkinter as tk
diff --git a/ch17-graphical-user-interfaces/5-working-with-widgets.py b/ch18-graphical-user-interfaces/5-working-with-widgets.py
similarity index 93%
rename from ch17-graphical-user-interfaces/5-working-with-widgets.py
rename to ch18-graphical-user-interfaces/5-working-with-widgets.py
index ca98a0c..3074995 100644
--- a/ch17-graphical-user-interfaces/5-working-with-widgets.py
+++ b/ch18-graphical-user-interfaces/5-working-with-widgets.py
@@ -1,4 +1,4 @@
-# 17.4 - Introduction to Tkinter
+# 18.4 - Introduction to Tkinter
 # Review exercises
 
 import tkinter as tk
diff --git a/ch17-graphical-user-interfaces/6-control-layout-with-geometry-managers.py b/ch18-graphical-user-interfaces/6-control-layout-with-geometry-managers.py
similarity index 98%
rename from ch17-graphical-user-interfaces/6-control-layout-with-geometry-managers.py
rename to ch18-graphical-user-interfaces/6-control-layout-with-geometry-managers.py
index 339c992..5c2869a 100644
--- a/ch17-graphical-user-interfaces/6-control-layout-with-geometry-managers.py
+++ b/ch18-graphical-user-interfaces/6-control-layout-with-geometry-managers.py
@@ -1,4 +1,4 @@
-# 17.6 - Control Layout With Geometry Managers
+# 18.6 - Control Layout With Geometry Managers
 # Review Exercise #2
 
 # NOTE: The first exercise in this section is instructional and does
diff --git a/ch17-graphical-user-interfaces/7-make-your-applications-interactive.py b/ch18-graphical-user-interfaces/7-make-your-applications-interactive.py
similarity index 94%
rename from ch17-graphical-user-interfaces/7-make-your-applications-interactive.py
rename to ch18-graphical-user-interfaces/7-make-your-applications-interactive.py
index f9e883f..6f2a39a 100644
--- a/ch17-graphical-user-interfaces/7-make-your-applications-interactive.py
+++ b/ch18-graphical-user-interfaces/7-make-your-applications-interactive.py
@@ -1,4 +1,4 @@
-# 17.7 - Make Your Applications Interactive
+# 18.7 - Make Your Applications Interactive
 # Review Exercises