diff --git a/documenting-python-code/README.md b/documenting-python-code/README.md
index 6a25540df6..eb40bfef14 100644
--- a/documenting-python-code/README.md
+++ b/documenting-python-code/README.md
@@ -40,7 +40,7 @@ say_hello(name)
 A dog says woof
 ```
 
-Print the column headers of an Excel spreadsheet:
+Print the column headers of a CSV or Excel spreadsheet:
 
 ```sh
 $ python spreadsheet_columns.py people.xlsx
diff --git a/documenting-python-code/animal.py b/documenting-python-code/animal.py
index 2d2ac999e7..d02ee69ae3 100644
--- a/documenting-python-code/animal.py
+++ b/documenting-python-code/animal.py
@@ -32,7 +32,7 @@ def __init__(self, name, sound, num_legs=4):
         sound : str
             The sound the animal makes
         num_legs : int, optional
-            The number of legs the animal (default is 4)
+            The number of legs the animal has (default is 4)
         """
 
         self.name = name
diff --git a/documenting-python-code/docstring_formats.py b/documenting-python-code/docstring_formats.py
index 2960ed9364..e2016f4071 100644
--- a/documenting-python-code/docstring_formats.py
+++ b/documenting-python-code/docstring_formats.py
@@ -19,7 +19,10 @@ def get_spreadsheet_cols_google(file_loc, print_cols=False):
         list: a list of strings representing the header columns
     """
 
-    file_data = pd.read_excel(file_loc)
+    if file_loc.lower().endswith(".csv"):
+        file_data = pd.read_csv(file_loc)
+    else:
+        file_data = pd.read_excel(file_loc)
     col_headers = list(file_data.columns.values)
 
     if print_cols:
@@ -40,7 +43,10 @@ def get_spreadsheet_cols_rest(file_loc, print_cols=False):
     :rtype: list
     """
 
-    file_data = pd.read_excel(file_loc)
+    if file_loc.lower().endswith(".csv"):
+        file_data = pd.read_csv(file_loc)
+    else:
+        file_data = pd.read_excel(file_loc)
     col_headers = list(file_data.columns.values)
 
     if print_cols:
@@ -65,7 +71,10 @@ def get_spreadsheet_cols_numpy(file_loc, print_cols=False):
         a list of strings representing the header columns
     """
 
-    file_data = pd.read_excel(file_loc)
+    if file_loc.lower().endswith(".csv"):
+        file_data = pd.read_csv(file_loc)
+    else:
+        file_data = pd.read_excel(file_loc)
     col_headers = list(file_data.columns.values)
 
     if print_cols:
@@ -86,7 +95,10 @@ def get_spreadsheet_cols_epytext(file_loc, print_cols=False):
     @returns: a list of strings representing the header columns
     """
 
-    file_data = pd.read_excel(file_loc)
+    if file_loc.lower().endswith(".csv"):
+        file_data = pd.read_csv(file_loc)
+    else:
+        file_data = pd.read_excel(file_loc)
     col_headers = list(file_data.columns.values)
 
     if print_cols:
diff --git a/documenting-python-code/spreadsheet_columns.py b/documenting-python-code/spreadsheet_columns.py
index 9abeb55137..b545594ba0 100644
--- a/documenting-python-code/spreadsheet_columns.py
+++ b/documenting-python-code/spreadsheet_columns.py
@@ -8,7 +8,8 @@
 (.xls, .xlsx) files.
 
 This script requires that `pandas` be installed within the Python
-environment you are running this script in.
+environment you are running this script in, along with `openpyxl` for
+.xlsx files and `xlrd` for .xls files.
 
 This file can also be imported as a module and contains the following
 functions:
@@ -36,10 +37,13 @@ def get_spreadsheet_cols(file_loc, print_cols=False):
     Returns
     -------
     list
-        a list of strings used that are the header columns
+        a list of strings that are the header columns
     """
 
-    file_data = pd.read_excel(file_loc)
+    if file_loc.lower().endswith(".csv"):
+        file_data = pd.read_csv(file_loc)
+    else:
+        file_data = pd.read_excel(file_loc)
     col_headers = list(file_data.columns.values)
 
     if print_cols:
@@ -49,7 +53,10 @@ def get_spreadsheet_cols(file_loc, print_cols=False):
 
 
 def main():
-    parser = argparse.ArgumentParser(description=__doc__)
+    parser = argparse.ArgumentParser(
+        description=__doc__,
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
     parser.add_argument(
         "input_file",
         type=str,
diff --git a/operator-function-overloading/custom_complex.py b/operator-function-overloading/custom_complex.py
index a0cd7c184b..aca1ffe8bd 100644
--- a/operator-function-overloading/custom_complex.py
+++ b/operator-function-overloading/custom_complex.py
@@ -1,12 +1,12 @@
-from math import hypot, atan, sin, cos
+from math import hypot, atan2, sin, cos
 
 
 class CustomComplex:
     """
     A class to represent a complex number, a+bj.
     Attributes:
-        real - int, representing the real part
-        imag - int, representing the imaginary part
+        real - int or float, representing the real part
+        imag - int or float, representing the imaginary part
 
     Implements the following:
 
@@ -41,17 +41,17 @@ def conjugate(self):
         Return:
             CustomComplex instance
         """
-        return CustomComplex(self.real, -self.imag)
+        return self.__class__(self.real, -self.imag)
 
     def argz(self):
         """
         Returns the argument of a complex number
         The argument is given by:
-            atan(imag_part/real_part)
+            atan2(imag_part, real_part)
         Return:
             float
         """
-        return atan(self.imag / self.real)
+        return atan2(self.imag, self.real)
 
     def __abs__(self):
         """
@@ -69,7 +69,7 @@ def __repr__(self):
         Return:
             str
         """
-        return f"CustomComplex({self.real}, {self.imag})"
+        return f"{self.__class__.__name__}({self.real}, {self.imag})"
 
     def __str__(self):
         """
@@ -87,15 +87,16 @@ def __add__(self, other):
         Return:
             CustomComplex instance
         """
-        if isinstance(other, float) or isinstance(other, int):
+        if isinstance(other, (int, float)):
             real_part = self.real + other
             imag_part = self.imag
-
-        if isinstance(other, CustomComplex):
+        elif isinstance(other, CustomComplex):
             real_part = self.real + other.real
             imag_part = self.imag + other.imag
+        else:
+            return NotImplemented
 
-        return CustomComplex(real_part, imag_part)
+        return self.__class__(real_part, imag_part)
 
     def __sub__(self, other):
         """
@@ -104,15 +105,16 @@ def __sub__(self, other):
         Return:
             CustomComplex instance
         """
-        if isinstance(other, float) or isinstance(other, int):
+        if isinstance(other, (int, float)):
             real_part = self.real - other
             imag_part = self.imag
-
-        if isinstance(other, CustomComplex):
+        elif isinstance(other, CustomComplex):
             real_part = self.real - other.real
             imag_part = self.imag - other.imag
+        else:
+            return NotImplemented
 
-        return CustomComplex(real_part, imag_part)
+        return self.__class__(real_part, imag_part)
 
     def __mul__(self, other):
         """
@@ -121,26 +123,27 @@ def __mul__(self, other):
         Return:
             CustomComplex instance
         """
-        if isinstance(other, int) or isinstance(other, float):
+        if isinstance(other, (int, float)):
             real_part = self.real * other
             imag_part = self.imag * other
-
-        if isinstance(other, CustomComplex):
+        elif isinstance(other, CustomComplex):
             real_part = (self.real * other.real) - (self.imag * other.imag)
             imag_part = (self.real * other.imag) + (self.imag * other.real)
+        else:
+            return NotImplemented
 
-        return CustomComplex(real_part, imag_part)
+        return self.__class__(real_part, imag_part)
 
     def __radd__(self, other):
         """
-        Same as __add__; allows 1 + CustomComplex('x+yj')
+        Same as __add__; allows 1 + CustomComplex(x, y)
         x + y == y + x
         """
         return self.__add__(other)
 
     def __rmul__(self, other):
         """
-        Same as __mul__; allows 2 * CustomComplex('x+yj')
+        Same as __mul__; allows 2 * CustomComplex(x, y)
         x * y == y * x
         """
         return self.__mul__(other)
@@ -156,11 +159,13 @@ def __rsub__(self, other):
         Return:
             CustomComplex instance
         """
-        if isinstance(other, float) or isinstance(other, int):
+        if isinstance(other, (int, float)):
             real_part = other - self.real
             imag_part = -self.imag
+        else:
+            return NotImplemented
 
-        return CustomComplex(real_part, imag_part)
+        return self.__class__(real_part, imag_part)
 
     def __eq__(self, other):
         """
@@ -171,6 +176,8 @@ def __eq__(self, other):
         Return:
             bool
         """
+        if not isinstance(other, (int, float, CustomComplex)):
+            return NotImplemented
         # Note: comparing floats directly is not a good idea in general
         # due to floating-point precision
         return (self.real == other.real) and (self.imag == other.imag)
@@ -184,6 +191,8 @@ def __ne__(self, other):
         Return:
             bool
         """
+        if not isinstance(other, (int, float, CustomComplex)):
+            return NotImplemented
         return (self.real != other.real) or (self.imag != other.imag)
 
     def __pow__(self, other):
@@ -204,4 +213,4 @@ def __pow__(self, other):
         real_part = round(r_raised * cos(argz_multiplied))
         imag_part = round(r_raised * sin(argz_multiplied))
 
-        return CustomComplex(real_part, imag_part)
+        return self.__class__(real_part, imag_part)
diff --git a/python-data-classes/position_make_dataclass.py b/python-data-classes/position_make_dataclass.py
index 5be429b501..a65f0e4164 100644
--- a/python-data-classes/position_make_dataclass.py
+++ b/python-data-classes/position_make_dataclass.py
@@ -1,3 +1,3 @@
 from dataclasses import make_dataclass
 
-Position = make_dataclass("Position", ["name", "lat", "lon"])
+Position = make_dataclass("Position", ["name", "lon", "lat"])
diff --git a/python-sql-libraries/README.md b/python-sql-libraries/README.md
index 70dec3de14..18a8c6d691 100644
--- a/python-sql-libraries/README.md
+++ b/python-sql-libraries/README.md
@@ -98,4 +98,4 @@ Query executed successfully
 Query executed successfully
 ```
 
-The script stops with a `DuplicateDatabase` error if `sm_app` already exists, so drop it before running the script again with `sudo -u postgres psql -c "DROP DATABASE sm_app"`.
+If `sm_app` already exists, the script reports the error and carries on, so the records are inserted a second time. To start over, drop the database with `sudo -u postgres psql -c "DROP DATABASE sm_app"`.
diff --git a/python-sql-libraries/mysql_app.py b/python-sql-libraries/mysql_app.py
index 70540732ff..8fa00b8a65 100644
--- a/python-sql-libraries/mysql_app.py
+++ b/python-sql-libraries/mysql_app.py
@@ -210,7 +210,7 @@ def execute_read_query(connection, query):
     UPDATE
       posts
     SET
-      description = "The weather has become pleasant now"
+      description = 'The weather has become pleasant now'
     WHERE
       id = 2
     """
diff --git a/python-sql-libraries/postgresql_app.py b/python-sql-libraries/postgresql_app.py
index e434b6c10e..1e56e91732 100644
--- a/python-sql-libraries/postgresql_app.py
+++ b/python-sql-libraries/postgresql_app.py
@@ -30,7 +30,7 @@ def create_database(connection, query):
     try:
         cursor.execute(query)
         print("Query executed successfully")
-    except OperationalError as e:
+    except psycopg2.Error as e:
         print(f"The error '{e}' occurred")
 
 
@@ -40,7 +40,7 @@ def execute_query(connection, query):
     try:
         cursor.execute(query)
         print("Query executed successfully")
-    except OperationalError as e:
+    except psycopg2.Error as e:
         print(f"The error '{e}' occurred")
 
 
@@ -51,7 +51,7 @@ def execute_read_query(connection, query):
         cursor.execute(query)
         result = cursor.fetchall()
         return result
-    except OperationalError as e:
+    except psycopg2.Error as e:
         print(f"The error '{e}' occurred")
 
 
@@ -180,7 +180,7 @@ def execute_read_query(connection, query):
     for user in users:
         print(user)
 
-    # Updating table records (PostgreSQL needs single quotes for strings)
+    # Updating table records
     update_post_description = """
     UPDATE
       posts
diff --git a/python-sql-libraries/sqlite_app.py b/python-sql-libraries/sqlite_app.py
index 9d79ec2016..8339298118 100644
--- a/python-sql-libraries/sqlite_app.py
+++ b/python-sql-libraries/sqlite_app.py
@@ -69,7 +69,7 @@ def execute_read_query(connection, query):
       text TEXT NOT NULL,
       user_id INTEGER NOT NULL,
       post_id INTEGER NOT NULL,
-      FOREIGN KEY (user_id) REFERENCES users (id)
+      FOREIGN KEY (user_id) REFERENCES users (id),
       FOREIGN KEY (post_id) REFERENCES posts (id)
     );
     """
@@ -79,7 +79,7 @@ def execute_read_query(connection, query):
       id INTEGER PRIMARY KEY AUTOINCREMENT,
       user_id INTEGER NOT NULL,
       post_id integer NOT NULL,
-      FOREIGN KEY (user_id) REFERENCES users (id)
+      FOREIGN KEY (user_id) REFERENCES users (id),
       FOREIGN KEY (post_id) REFERENCES posts (id)
     );
     """
@@ -105,12 +105,12 @@ def execute_read_query(connection, query):
     INSERT INTO
       posts (title, description, user_id)
     VALUES
-      ("Happy", "I am feeling very happy today", 1),
-      ("Hot Weather", "The weather is very hot today", 2),
-      ("Help", "I need some help with my work", 2),
-      ("Great News", "I am getting married", 1),
-      ("Interesting Game", "It was a fantastic game of tennis", 5),
-      ("Party", "Anyone up for a late-night party today?", 3);
+      ('Happy', 'I am feeling very happy today', 1),
+      ('Hot Weather', 'The weather is very hot today', 2),
+      ('Help', 'I need some help with my work', 2),
+      ('Great News', 'I am getting married', 1),
+      ('Interesting Game', 'It was a fantastic game of tennis', 5),
+      ('Party', 'Anyone up for a late-night party today?', 3);
     """
 
     execute_query(connection, create_posts)
@@ -228,7 +228,7 @@ def execute_read_query(connection, query):
     UPDATE
       posts
     SET
-      description = "The weather has become pleasant now"
+      description = 'The weather has become pleasant now'
     WHERE
       id = 2
     """