Exception Handling.md

Exception Handling

Exception Handling allows us to handle errors and unexpected situations that may occur during program execution.

Handling and Raising Exceptions:

Exceptions are raised when an error or exceptional condition occurs during the execution of a program. Python provides a way to handle these exceptions using try-except blocks.

The basic structure of a try-except block is as follows:

try:
    # Code that might raise an exception
except ExceptionType:
    # Code to handle the exception

In this structure, the code within the try block is executed. If an exception of the specified ExceptionType is raised within the try block, the program jumps to the corresponding except block, where we can handle the exception.

Let's see an example:

try:
    x = 10 / 0
except ZeroDivisionError:
    print("Error: Division by zero!")

In this example, we attempt to divide the number 10 by zero, which raises a ZeroDivisionError. The program then jumps to the except block, where we print an error message indicating the division by zero.

We can also raise exceptions manually using the raise keyword. This is useful when we want to indicate an exceptional condition in our code. Here's an example:

x = -1
if x < 0:
    raise ValueError("Invalid value: x must be positive.")

In this example, we raise a ValueError exception if the value of x is negative. The ValueError exception is created with a custom error message that provides information about the exceptional condition.

try-except-else-finally Blocks:

In addition to the try and except blocks, Python provides two optional blocks: else and finally.

The else block is executed only if no exception occurs within the try block. It is useful for performing actions that should be executed when no errors are encountered.

The finally block is always executed, regardless of whether an exception occurs or not. It is used for releasing resources or performing cleanup operations that need to be executed regardless of the outcome of the try block.

Here's an example that demonstrates the usage of try, except, else, and finally blocks:

try:
    x = 10 / 2
except ZeroDivisionError:
    print("Error: Division by zero!")
else:
    print("The division was successful.")
finally:
    print("End of try-except-else-finally block.")

In this example, the division operation within the try block is successful, so the program executes the else block and prints a success message. Finally, the program executes the finally block to signal the end of the entire try-except-else-finally block.