How does Python handle exceptions?

In Python, exceptions are handled using try-except blocks. This mechanism allows you to catch and manage errors that occur during program execution, preventing the program from crashing. Here’s a breakdown of how Python handles exceptions:

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1. Basic Structure of Try-Except:

try:
    # Code that might raise an exception
    risky_code()
except ExceptionType:
    # Code to handle the exception
    print("An error occurred.")

• try block: Contains the code that might throw an exception.
• except block: Contains the code to handle specific exceptions.

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2. Handling Specific Exceptions:

You can handle specific types of exceptions to address them appropriately.

try:
    result = 10 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")

Here, only a ZeroDivisionError will be caught.

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3. Catching Multiple Exceptions:

You can handle multiple exceptions either by listing them in a tuple or using multiple except blocks.

try:
    risky_code()
except (ValueError, KeyError) as e:
    print(f"Caught a ValueError or KeyError: {e}")

try:
    risky_code()
except ValueError:
    print("ValueError occurred.")
except KeyError:
    print("KeyError occurred.")

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4. Catching All Exceptions:

To catch all exceptions, use except Exception or a bare except (not recommended).

try:
    risky_code()
except Exception as e:
    print(f"An unexpected error occurred: {e}")

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5. The Else Clause:

The else block runs if the try block does not raise any exception.

try:
    result = 10 / 2
except ZeroDivisionError:
    print("You can't divide by zero!")
else:
    print(f"Result is {result}")

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6. The Finally Clause:

The finally block is used to execute code regardless of whether an exception was raised or not. It’s often used for cleanup operations.

try:
    risky_code()
except Exception:
    print("An error occurred.")
finally:
    print("This will always execute.")

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7. Raising Exceptions:

You can raise exceptions explicitly using the raise keyword.

if age < 0:
    raise ValueError("Age cannot be negative!")

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8. Custom Exceptions:

You can define custom exceptions by subclassing the Exception class.

class CustomError(Exception):
    pass

try:
    raise CustomError("This is a custom error!")
except CustomError as e:
    print(e)

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Summary:

Python’s exception handling mechanism is flexible and powerful, allowing developers to:

• Anticipate errors.
• Provide specific responses to different errors.
• Ensure resources are cleaned up properly.

This promotes robust and maintainable code.