DevOps Classroom notes 22/Oct/2025

Dealing with json and yaml files

• For json we have a standard libarary module json
• For yaml we need to use a pypi package pyyaml

uv add pyyaml

• Refer Here for the changes
• Refer Here for the notebook

Databases

• Databases handle storing and retreival of data.
• Databases are of different types, on a larger note
  • Relational Databases
  • NOSQL Databases
• Relational Databases use a Standard called as SQL to manage the data and the companies that use this Standard and built database management systems
  • Microsoft SQL Server
  • Oracle
  • mysql
  • postgres
  • db2
  • sqlite
• Relational databases use Tables which can have relationships between them

Designing tables

• Problem: Students joining courses
  
• SQL:
  • Create
  • Retrieve
  • Update
  • Delete
• Create Tables

Database	SQL Syntax
MySQL	sql CREATE TABLE student ( sno INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(100) NOT NULL, phone VARCHAR(15), email VARCHAR(100) UNIQUE );
PostgreSQL	sql CREATE TABLE student ( sno SERIAL PRIMARY KEY, name VARCHAR(100) NOT NULL, phone VARCHAR(15), email VARCHAR(100) UNIQUE );
SQLite	sql CREATE TABLE student ( sno INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, phone TEXT, email TEXT UNIQUE );
SQL Server	sql CREATE TABLE student ( sno INT IDENTITY(1,1) PRIMARY KEY, name NVARCHAR(100) NOT NULL, phone NVARCHAR(15), email NVARCHAR(100) UNIQUE );
Oracle	sql CREATE TABLE student ( sno NUMBER GENERATED ALWAYS AS IDENTITY PRIMARY KEY, name VARCHAR2(100) NOT NULL, phone VARCHAR2(15), email VARCHAR2(100) UNIQUE );

• Insert records

Database	SQL Syntax
MySQL	sql INSERT INTO student (name, phone, email) VALUES ('Tony Stark', '9998887776', 'tony@starkindustries.com'), ('Steve Rogers', '9991112223', 'steve@avengers.com'), ('Natasha Romanoff', '8885554442', 'natasha@shield.org');
PostgreSQL	sql INSERT INTO student (name, phone, email) VALUES ('Tony Stark', '9998887776', 'tony@starkindustries.com'), ('Steve Rogers', '9991112223', 'steve@avengers.com'), ('Natasha Romanoff', '8885554442', 'natasha@shield.org');
SQLite	sql INSERT INTO student (name, phone, email) VALUES ('Tony Stark', '9998887776', 'tony@starkindustries.com'); INSERT INTO student (name, phone, email) VALUES ('Steve Rogers', '9991112223', 'steve@avengers.com'); INSERT INTO student (name, phone, email) VALUES ('Natasha Romanoff', '8885554442', 'natasha@shield.org');
SQL Server	sql INSERT INTO student (name, phone, email) VALUES ('Tony Stark', '9998887776', 'tony@starkindustries.com'), ('Steve Rogers', '9991112223', 'steve@avengers.com'), ('Natasha Romanoff', '8885554442', 'natasha@shield.org');
Oracle	sql INSERT INTO student (name, phone, email) VALUES ('Tony Stark', '9998887776', 'tony@starkindustries.com'); INSERT INTO student (name, phone, email) VALUES ('Steve Rogers', '9991112223', 'steve@avengers.com'); INSERT INTO student (name, phone, email) VALUES ('Natasha Romanoff', '8885554442', 'natasha@shield.org'); COMMIT;

• In modern day programming we prefer ORMs (Object Relational Mapping) where we interact with Objects rather than tables & ORM frameworks deal with different databases with same code written. Popular ORM Frameworks
  • Java -> Hibernate
  • C# -> Entity Framework
  • Python -> SQL Alchemy, Django-ORM

Errors & Exception Handling

• Both Errors and Exceptions are deviations from ideal behavior, whereas Errors cannot be handled by program & Exceptions can be
• In python we have a hierarchy of Exceptions

BaseException
├─ SystemExit
├─ KeyboardInterrupt
├─ GeneratorExit
└─ Exception
   ├─ ArithmeticError
   │  ├─ FloatingPointError
   │  ├─ OverflowError
   │  └─ ZeroDivisionError
   ├─ AssertionError
   ├─ AttributeError
   ├─ BufferError
   ├─ EOFError
   ├─ ImportError
   │  └─ ModuleNotFoundError
   ├─ LookupError
   │  ├─ IndexError
   │  └─ KeyError
   ├─ MemoryError
   ├─ NameError
   │  └─ UnboundLocalError
   ├─ OSError
   │  ├─ BlockingIOError
   │  ├─ ChildProcessError
   │  ├─ ConnectionError
   │  │  ├─ BrokenPipeError
   │  │  ├─ ConnectionAbortedError
   │  │  ├─ ConnectionRefusedError
   │  │  └─ ConnectionResetError
   │  ├─ FileExistsError
   │  ├─ FileNotFoundError
   │  ├─ InterruptedError
   │  ├─ IsADirectoryError
   │  ├─ NotADirectoryError
   │  ├─ PermissionError
   │  ├─ ProcessLookupError
   │  └─ TimeoutError
   ├─ ReferenceError
   ├─ RuntimeError
   │  ├─ NotImplementedError
   │  └─ RecursionError
   ├─ StopAsyncIteration
   ├─ StopIteration
   ├─ SyntaxError
   │  └─ IndentationError
   │     └─ TabError
   ├─ SystemError
   ├─ TypeError
   ├─ ValueError
   │  └─ UnicodeError
   │     ├─ UnicodeDecodeError
   │     ├─ UnicodeEncodeError
   │     └─ UnicodeTranslateError
   └─ Warning
      ├─ DeprecationWarning
      ├─ PendingDeprecationWarning
      ├─ RuntimeWarning
      ├─ SyntaxWarning
      ├─ UserWarning
      ├─ FutureWarning
      ├─ ImportWarning
      ├─ UnicodeWarning
      ├─ BytesWarning
      ├─ ResourceWarning
      └─ EncodingWarning

• Lets write a simple divide function

def divide(a:int, b:int) -> float:
    return a/b

• Now lets call this function with b as 0

divide(4,0)

• We can handle errors by try, except, finally blocks