Python Exception Handling

Exception Handling

• Exception handling is a technique used to manage errors in programs.
• Errors that occur in programs are known as exceptions.
• Exceptions can occur due to user inputs, incorrect data types, or other runtime conditions.
• The try, except, else, and finally blocks are used to handle exceptions in Python.
• The try block contains the code you want to execute, the except block handles potential exceptions, the else block executes if no exceptions occur, and the finally block always executes regardless of exceptions.

Types of Exceptions

• Built-in exceptions: These are predefined exceptions provided by Python, such as ZeroDivisionError, ValueError, IndexError, NameError, TypeError, and IOError.
• User-defined exceptions: Programmers can create custom exception classes to handle specific error scenarios based on their application's needs.

Handling Exceptions

• Use a try block to enclose the code that might raise an exception.
• Use an except block to catch and handle the specific exception you expect.
• Use an else block to execute code when no exception occurs within the try block.
• Use a finally block to execute code regardless of whether an exception occurred or not.

Example of Exception Handling

• You can divide a number by another number using the division operator (/) in Python.
• However, dividing by zero will result in a ZeroDivisionError exception.
• To handle this, you can use a try block to attempt the division, an except block to catch ZeroDivisionError, and an else block to execute code when the division is successful.

User-Defined Exception Example

• In the example, a custom exception class named 'TenError' is created to handle a specific scenario where the user inputs the number '10' as input for the variable 'number2'.
• The 'raise' keyword is used to trigger the custom exception when 'number2' equals '10'.
• This allows you to handle specific error scenarios and provide more customized error messages.

Exception Handling

• A technique used to manage errors in programs
• Errors that occur in programs are called exceptions
• Exceptions can happen due to various reasons including incorrect user input, data type mismatches, and runtime issues.
• Python uses special blocks: try, except, else, and finally for exception management.
• try block encloses code that might raise an exception
• except block handles specific exceptions
• else block executes if no exceptions occur within the try block
• finally block always executes regardless of exceptions.

Types of Exceptions

• Built-in Exceptions: Predefined exceptions provided by Python. Examples include:
  • ZeroDivisionError: Trying to divide by zero
  • ValueError: Invalid data type or value.
  • IndexError: Access to an index that doesn't exist in a sequence
  • NameError: Trying to access a variable that hasn't been defined.
  • TypeError: Using incorrect data type for an operation
  • IOError: Error related to input/output operations (e.g., file reading/writing).
• User-defined Exceptions: Programmers can create custom exception classes to address specific error scenarios based on their application's needs.

Handling Exceptions

• When using try block, the code within might encounter an exception.
• except block catches and handles the anticipated exception. This allows the program to continue executing, instead of crashing.
• else block runs when no exceptions are detected in the try block
• finally block ensures specific code is executed whether or not an exception occurs, it's often used for resource cleanup (e.g., closing files).

Example of Exception Handling

• The code example demonstrates managing the ZeroDivisionError exception, which is a critical issue in division.
• The try block attempts the division operation.
• The except block catches the ZeroDivisionError, providing a user-friendly message if it occurs.
• The else block handles the scenario where the division is successful and displays the result.

User-Defined Exception Example

• The example shows how to create a custom exception class named 'TenError' to handle situations where the variable 'number2' has the specific value '10'.
• The raise keyword is used to trigger the custom exception when the condition is met.
• This approach allows for more specific error handling and tailored error messages, making the program more robust and user friendly.

This quiz focuses on exception handling in Python. It covers the techniques for managing errors, types of exceptions, and the structure of try, except, else, and finally blocks. Test your knowledge on built-in and user-defined exceptions.