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Error Handling

Python uses try/except blocks for error handling.

The basic structure is:

try:
    # Code that may raise an exception
except ExceptionType:
    # Code to handle the exception
finally:
    # Code executes all the time

Uses

Improved User Experience: Instead of the program crashing, you can provide a user-friendly error message.

Debugging: Capturing exceptions can help you log errors and understand what went wrong.

Program Continuity: Allows the program to continue running or perform cleanup operations before terminating.

Guaranteed Cleanup: Ensures that certain operations, like closing files or releasing resources, are always performed.

Some key points

• You can catch specific exception types or use a bare except to catch any exception.

• Multiple except blocks can be used to handle different exceptions.

• An else clause can be added to run if no exception occurs.

• A finally clause will always execute, whether an exception occurred or not.

Without Try/Except

x = 10 / 0 

Basic Try/Except

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

Generic Exception

try:
    file = open("nonexistent_file.txt", "r")
except:
    print("An error occurred!")

Find the exact error

try:
    file = open("nonexistent_file.txt", "r")
except Exception as e:
    print(str(e))

Raise - Else and Finally

try:
    x = -10
    if x <= 0:
        raise ValueError("Number must be positive")
except ValueError as ve:
    print(f"Error: {ve}")
else:
    print(f"You entered: {x}")
finally:
    print("This will always execute")

try:
    x = 10
    if x <= 0:
        raise ValueError("Number must be positive")
except ValueError as ve:
    print(f"Error: {ve}")
else:
    print(f"You entered: {x}")
finally:
    print("This will always execute")

Nested Functions

def divide(a, b):
    try:
        result = a / b
        return result
    except ZeroDivisionError:
        print("Error in divide(): Cannot divide by zero!")
        raise  # Re-raise the exception

def calculate_and_print(x, y):
    try:
        result = divide(x, y)
        print(f"The result of {x} divided by {y} is: {result}")
    except ZeroDivisionError as e:
        print(str(e))
    except TypeError as e:
        print(str(e))

# Test the nested error handling
print("Example 1: Valid division")
calculate_and_print(10, 2)

print("\nExample 2: Division by zero")
calculate_and_print(10, 0)

print("\nExample 3: Invalid type")
calculate_and_print("10", 2)

#errorhandling #exception #tryVer 5.5.3