Course Topics
Python Basics Introduction and Setup Syntax and Indentation Comments and Documentation Running Python Programs Exercise Variables and Data Types Variables and Assignment Numbers (int, float, complex) Strings and Operations Booleans and None Type Conversion Exercise Operators Arithmetic Operators Comparison Operators Logical Operators Assignment Operators Bitwise Operators Exercise Input and Output Getting User Input Formatting Output Print Function Features Exercise Control Flow - Conditionals If Statements If-Else Statements Elif Statements Nested Conditionals Exercise Control Flow - Loops For Loops While Loops Loop Control (break, continue) Nested Loops Exercise Data Structures - Lists Creating and Accessing Lists List Methods and Operations List Slicing List Comprehensions Exercise Data Structures - Tuples Creating and Accessing Tuples Tuple Methods and Operations Tuple Packing and Unpacking Exercise Data Structures - Dictionaries Creating and Accessing Dictionaries Dictionary Methods and Operations Dictionary Comprehensions Exercise Data Structures - Sets Creating and Accessing Sets Set Methods and Operations Set Comprehensions Exercise Functions Defining Functions Function Parameters and Arguments Return Statements Scope and Variables Lambda Functions Exercise String Manipulation String Indexing and Slicing String Methods String Formatting Regular Expressions Basics Exercise File Handling Opening and Closing Files Reading from Files Writing to Files File Modes and Context Managers Exercise Error Handling Understanding Exceptions Try-Except Blocks Finally and Else Clauses Raising Custom Exceptions Exercise Object-Oriented Programming - Classes Introduction to OOP Creating Classes and Objects Instance Variables and Methods Constructor Method Exercise Object-Oriented Programming - Advanced Inheritance Method Overriding Class Variables and Methods Static Methods Exercise Modules and Packages Importing Modules Creating Custom Modules Python Standard Library Installing External Packages Exercise Working with APIs and JSON Making HTTP Requests JSON Data Handling Working with REST APIs Exercise Database Basics Introduction to Databases SQLite with Python CRUD Operations Exercise Final Project Project Planning Building Complete Application Code Organization Testing and Debugging Exercise

SQLite with Python

Introduction

  • Why this topic matters: SQLite is a lightweight, standalone database that's great for small to medium-sized projects and applications. By understanding how to interact with SQLite using Python, you'll be able to manage and analyze data more efficiently.
  • What you'll learn: We'll explore the basics of SQLite, including creating tables, inserting data, querying data, updating records, and handling errors.

Core Concepts

  • Database: A database is a collection of data organized in tables. In SQLite, the entire database is stored as a single file.
  • Table: Tables hold structured data and consist of rows (records) and columns (fields). Each table has a unique name and a defined schema, which specifies the names and types of its columns.
  • SQL: Structured Query Language (SQL) is a standard language used to communicate with databases and perform various operations like creating tables, inserting data, querying, updating, and deleting records.

Practical Examples

Let's create a simple SQLite database using Python and manage its data:

import sqlite3

# Connect to the database or create it if it doesn't exist
conn = sqlite3.connect('example.db')
cursor = conn.cursor()

# Create a table called 'users' with columns 'id', 'name', and 'email'
cursor.execute('''CREATE TABLE IF NOT EXISTS users (
                     id INTEGER PRIMARY KEY,
                     name TEXT NOT NULL,
                     email TEXT UNIQUE NOT NULL);''')

# Insert data into the 'users' table
cursor.execute("INSERT INTO users (name, email) VALUES ('John Doe', 'john@example.com');")
conn.commit()

# Query data from the 'users' table
cursor.execute('SELECT * FROM users;')
result = cursor.fetchall()
for row in result:
    print(row)

# Update a record in the 'users' table
cursor.execute("UPDATE users SET name = 'Jane Doe' WHERE id=1;")
conn.commit()

Common Issues and Solutions (CRITICAL SECTION)

NameError

What causes it: Misspelling a variable or function name.

# Bad code example
connecion = sqlite3.connect('example.db')

Error message:

NameError: name 'connecion' is not defined

Solution: Correct the spelling of the variable or function name.

# Corrected code
conn = sqlite3.connect('example.db')

Why it happens: Python cannot find a variable or function with the specified name, because it is misspelled or not defined.
How to prevent it: Double-check your spelling and make sure you are using the correct names for variables and functions.

TypeError

What causes it: Trying to perform an incompatible operation on different data types.

# Bad code example
cursor.execute("UPDATE users SET name = 123;")

Error message:

TypeError: not all arguments converted during string formatting

Solution: Use the appropriate data type for each column in SQL statements.

# Corrected code
cursor.execute("UPDATE users SET name = '123';")

Why it happens: Python tries to convert different data types to a common format, but fails because of an incompatible operation.
How to prevent it: Ensure that the data type you are using for each column in SQL statements is compatible with its expected data type in the database schema.

Best Practices

  • Close connections: Always close the database connection after you're done using it, to free up system resources.
    python conn.close()
  • Use transactions: Wrap multiple operations within a single transaction to ensure data consistency in case of an error.
    python cursor.execute("BEGIN TRANSACTION;") # Multiple SQL operations go here cursor.execute("COMMIT;")
  • Error handling: Use try/except blocks to catch and handle errors gracefully, instead of letting them propagate up the call stack.
    python try: # SQL operation that might raise an error except Error as e: print(e)

Key Takeaways

  • Understand the basics of SQLite: Create tables, insert data, query data, update records, and handle errors.
  • Follow best practices: Close connections, use transactions, and handle errors gracefully.
  • Next steps for learning: Learn more advanced SQLite features such as views, triggers, and indexes; explore other database management systems like PostgreSQL or MySQL.
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