Exception & Error Handling

Handling exceptions lets your program respond to unexpected conditions without crashing.

try / except / finally

try:
    value = int(user_input)
except ValueError:
    print("Invalid number")
else:
    print("Parsed OK")
finally:
    print("Always runs")

Raising Exceptions

Use raise to signal an error:

if value < 0:
    raise ValueError("value must be non-negative")

Custom Exceptions

Create a specific exception type for domain errors:

class ValidationError(Exception):
    pass

raise ValidationError("bad input")

Best Practices

• Catch specific exception types.
• Log errors with context.
• Use finally or context managers for cleanup.