Python Modules, Classes & Objects Explained

1. Python Code Architecture: Module → Class → Object → Method / Attribute

Before reading individual Python statements, first understand the architecture. A Python program is easier to read when you identify which layer each name belongs to.

For the first learner example, the architecture is:

pathlib → Path → folder → mkdir() └──→ name

Architecture of a Larger Python Program

When the program becomes larger, such as your SQL Server setup program, the same idea sits inside a broader program structure:

2. The Five Python Terms You Must Understand First

Start with this one table. It gives you a practical mental model for reading Python code.

3. Your First Code: pathlib → Path → folder → mkdir() → name

from pathlib import Path folder = Path(r"D:\SQF_Reports")
folder.mkdir(exist_ok=True) print(folder.name)

This small program is enough to understand the basic structure used later in larger automation and reporting projects.

4. What Is a Module in Python?

A module is reusable Python code that can contain functions, classes, variables and other definitions. We import a module or something from a module so we can use code that has already been written.

from pathlib import Path

Here, pathlib is the module. It provides tools for working with file-system paths. We are importing one specific tool from it: the Path class.

A simple way to remember it is:

Two common import styles

import pathlib folder = pathlib.Path(r"D:\SQF_Reports")

Or import only the class you need:

from pathlib import Path folder = Path(r"D:\SQF_Reports")

Both are valid. For a first learner program, from pathlib import Path keeps the later code shorter and easier to read.

5. What Is a Class in Python?

A class is a blueprint used to create objects. In this lesson, Path is the class.

Path

The class defines how a path object behaves and what operations are available to it. You normally do not need to know the internal code of the class to use it.

6. What Is an Object in Python?

An object is the actual value created from a class. Here:

folder = Path(r"D:\SQF_Reports")

Path is the class and folder is the variable that refers to the resulting Path object.

Think of the relationship as:

Class Object
Path → folder

One class can be used to create many objects:

report_folder = Path(r"D:\SQF_Reports")
backup_folder = Path(r"D:\SQF_Backup")

Both objects are created from the same Path class, but they represent different paths.

7. What Is a Method in Python?

A method is an action associated with an object. Methods are normally called using parentheses.

folder.mkdir(exist_ok=True)

Read this from left to right:

• folder → the object
• . → access something belonging to that object
• mkdir → the method name
• () → call or execute the method
• exist_ok=True → allow the folder to already exist without raising an error

8. What Is an Attribute in Python?

An attribute is information or a property associated with an object. It is commonly accessed without parentheses.

folder.name

If folder represents D:\SQF_Reports, then:

print(folder.name)

prints:

SQF_Reports

Compare the two:

9. Read the Complete Code Like an Engineer

from pathlib import Path folder = Path(r"D:\SQF_Reports")
folder.mkdir(exist_ok=True) print(folder.name)

1. Import: Get the Path class from the pathlib module.
2. Create object: Use Path(...) to create a path object and store it in folder.
3. Call method: Use folder.mkdir(...) to create the directory if required.
4. Read attribute: Use folder.name to get the final folder name.
5. Display: Use the built-in print() function to show that value.

10. How This Helps with datetime, pandas, pyodbc and openpyxl

After the five basic terms are clear, larger import statements become easier to understand.

You do not need to master these libraries in Lesson 1. The goal is to recognize the structure when you meet them in later SQL Server and Excel-reporting labs.

11. Final Practical: Identify Module, Class, Object, Method and Attribute in Your SQL Server Code

Now apply the same architecture to a real program. This script creates SQF_DB, creates dbo.tblEvent when required, verifies the table and handles SQL Server errors.

Your Code with Architecture Comments

"""Create SQF_DB and dbo.tblEvent when they do not already exist.""" import pyodbc # MODULE: pyodbc SERVER = r"SOFTWELL\WINCC" # Variable / configuration constant
DATABASE = "SQF_DB" # Variable / configuration constant
DRIVER = "ODBC Driver 17 for SQL Server" # Variable / configuration constant def connect(database_name, *, autocommit=False): # FUNCTION: user-defined function return pyodbc.connect( # FUNCTION: connect() belongs to pyodbc module f"DRIVER={{{DRIVER}}};" f"SERVER={SERVER};" f"DATABASE={database_name};" "Trusted_Connection=yes;" "TrustServerCertificate=yes;", autocommit=autocommit, # Function argument, NOT an attribute timeout=15, # Function argument ) # RETURNS: a Connection OBJECT def create_database(): # FUNCTION # DATABASE is a trusted constant. SQL identifiers cannot use ? parameters. with connect("master", autocommit=True) as connection: # connection = OBJECT (Connection object returned by pyodbc.connect) cursor = connection.cursor() # connection.cursor() = METHOD of the connection OBJECT # cursor = OBJECT (Cursor object returned by the cursor() method) cursor.execute(f""" IF DB_ID(N'{DATABASE}') IS NULL BEGIN CREATE DATABASE [{DATABASE}]; END; """) # cursor.execute() = METHOD of the cursor OBJECT def create_event_table(): # FUNCTION with connect(DATABASE) as connection: # connection = OBJECT cursor = connection.cursor() # cursor() = METHOD # cursor = OBJECT cursor.execute(""" IF OBJECT_ID(N'dbo.tblEvent', N'U') IS NULL BEGIN CREATE TABLE dbo.tblEvent ( DT datetime NOT NULL, TM varchar(10) NULL, SQF_No int NULL, ChargeNo varchar(50) NULL, Event_From varchar(100) NULL, Event_To varchar(100) NULL, Temp_Set float NULL, Temp_Act float NULL, Cp_Set float NULL, Cp_Act float NULL, Oil_Set float NULL, Oil_Act float NULL, Jacket_Set float NULL, Jacket_Act float NULL, Fan_Status varchar(10) NULL ); END; """) # execute() = METHOD of cursor OBJECT connection.commit() # commit() = METHOD of connection OBJECT def verify_objects(): # FUNCTION with connect(DATABASE) as connection: # connection = OBJECT cursor = connection.cursor() # cursor = OBJECT; cursor() = METHOD cursor.execute(""" SELECT DB_NAME() AS DatabaseName, OBJECT_ID(N'dbo.tblEvent', N'U') AS TableObjectId; """) # execute() = METHOD database_name, table_object_id = cursor.fetchone() # fetchone() = METHOD of cursor OBJECT # database_name and table_object_id = values returned from the query row if table_object_id is None: raise RuntimeError("dbo.tblEvent was not created.") # RuntimeError = built-in exception CLASS return database_name, table_object_id def main(): # FUNCTION: program controller try: create_database() # FUNCTION call print(f"Database [{DATABASE}] is available.") create_event_table() # FUNCTION call print("Table [dbo].[tblEvent] is available.") database_name, table_object_id = verify_objects() # FUNCTION call print(f"Verified database: {database_name}") print(f"Verified table object ID: {table_object_id}") except pyodbc.Error as error: # pyodbc = MODULE # Error = exception CLASS provided by pyodbc # error = exception OBJECT created when a pyodbc error occurs raise SystemExit(f"SQL Server setup failed: {error}") from error # SystemExit = built-in exception CLASS if __name__ == "__main__": # __name__ = special module-level variable used to detect direct execution main() # ============================================================
# FINAL OOP IDENTIFICATION FOR LEARNERS
# ============================================================
# MODULE : pyodbc
#
# CLASS : pyodbc.Error
# Connection and Cursor are the runtime object types used by pyodbc.
#
# OBJECT : connection
# cursor
# error
#
# METHOD : connection.cursor()
# cursor.execute(...)
# connection.commit()
# cursor.fetchone()
#
# ATTRIBUTE : The current program does not directly read a pyodbc object attribute.
# Examples for learning only:
# connection.autocommit # property/attribute of a Connection object
# cursor.rowcount # attribute of a Cursor object
#
# FUNCTION : pyodbc.connect(...)
# connect()
# create_database()
# create_event_table()
# verify_objects()
# main()
#
# IMPORTANT : Function and Method are not the same.
# pyodbc.connect() -> module-level FUNCTION
# connection.cursor() -> object METHOD
# cursor.execute() -> object METHOD