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By Kevin McAleer, 3 Minutes
Module 8 covers the important topics of database transactions and error handling in SQLite. You will learn how to work with transactions to ensure data integrity and handle errors effectively in your Python code.
A database transaction is a logical unit of work that consists of one or more database operations. Transactions ensure that a group of database operations are executed as a single, atomic unit. If any part of the transaction fails, all changes made within the transaction can be rolled back.
Transactions in databases follow the ACID properties:
SQLite provides support for transactions through the BEGIN, COMMIT, and ROLLBACK statements.
BEGIN
COMMIT
ROLLBACK
To start a transaction, we use the BEGIN statement.
# Begin a transaction connection.execute("BEGIN")
By default, SQLite starts a transaction automatically for each individual SQL statement. However, explicitly beginning a transaction allows us to group multiple SQL statements into a single transaction.
To commit the changes made within a transaction, we use the COMMIT statement.
# Commit a transaction connection.execute("COMMIT")
By committing a transaction, we make the changes permanent and ensure their durability.
If an error occurs or we want to discard the changes made within a transaction, we can roll back the transaction using the ROLLBACK statement.
# Roll back a transaction connection.execute("ROLLBACK")
Rolling back a transaction undoes any changes made within the transaction, restoring the database to its state before the transaction began.
When working with databases, it’s crucial to handle potential errors gracefully. SQLite provides error handling mechanisms through Python’s exception handling.
To catch and handle SQLite errors, we can use the try and except statements in Python.
try
except
try: # Database operations connection.execute("...") # ... except sqlite3.Error as e: # Handle the exception print(f"An error occurred: {e}")
By incorporating exception handling, we can provide informative error messages and take appropriate actions in case of any issues.
By default, SQLite operates in auto-commit mode, where each SQL statement is treated as a separate transaction. However, explicitly using transactions can provide additional control and ensure the integrity of related operations.
In SQLite, changes made within a transaction are guaranteed to be atomic. When a transaction is committed, the changes are durable and survive any subsequent system failures.
By understanding database transactions and error handling in SQLite, you will have the knowledge to manage data changes effectively, maintain data integrity, and handle errors in your Python code.
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