04. error handling.md

Error Handling

• a crucial aspect of writing robust and reliable programs
• involves identifying, handling, and potentially recovering from errors or exceptions that may occur during the execution of a Python program
• Errors can occur for various reasons, such as incorrect input, file not found, division by zero, and many others. Python provides several mechanisms for error handling

1. exceptions
   • in Python, errors are represented as exceptions
   • when an error occurs, an exception object is raised, and the program stops executing unless the exception is caught and handled
2. Try-Except Blocks
   • the most common way to handle exceptions is by using try-except blocks
   • enclose the code that might raise an exception within a try block, and you specify the handling code in an except block

   try:
       # Code that may raise an exception
   except SomeException:
       # Code to handle the exception

   • example:

     try:
         result = 10 / 0 # This will raise a ZeroDivisionError
     except ZeroDivisionError as e:
         pritn(f"Error: {e}")

3. Multiple Except Blocks
   • can use multiple except blocks to handle different types of exceptions
   • python allows you to catch and handle different exceptions in separate blocks

   try:
       # Code that may raise an exception
   except FirstException:
       # Code to handle the first exception
   except SecondException:
       # Code to handle the second exception

4. Else Clause
   • can use an else clause in a try-except block to specify code that should be executed if no exceptions are raised

   try:
       # Code that may raise an exception
   except SomeException:
       # Code to handle the exception
   else:
       # Code to execute if no exception is raised

5. Finally Block
   • the finally block is used to specify code that should be executed regardless of whether an exception was raised or not
   • it is commonly used for cleanup operations

   try:
       # Code that may raise an exception
   except SomeException:
       # Code to handlethe exception
   finally:
       # Code that always runs, even is an exception was raised

6. Custom Exceptions
   • can create your own custom exception classes by inheriting from the Exception class or one of its subclasses
   • allows to define specific exceptions tailored to your application

   class CustomError(Exception):
       pass

7. Raising Exceptions
   • can raise exceptions explicitly using the raise statement, allowing you to signal errors or exceptional conditions in your code

   if condition:
       raise CustomError("This is a custom error message")

8. Exception Hierarchy
   • Python has a built-in exception hierarchy with a base class BaseException at the top
   • more specific exception classes are derived from it
   • This hierarchy allows to catch exceptions at different levels of granularity
     • granularity: 세분성. 무언가를 더 작은 단위로 표현하는 것을 말함
9. Common Exception Types
   • Python has several built-in exception types, including ZeroDivisionError, ValueError, FileNotFoundError, and TypeError, among others
   • Understanding these exception types can help you handle errors effectively.
10. Logging
    • can use the Python logging module to log error messages and other information to a log file or the console, helping with debugging and monitoring