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Error handling · easy

15. Exceptions

try/except/else/finally for handling errors.

Errors are raised as exceptions and caught with `try`/`except`. `else` runs if no exception occurred; `finally` always runs.

python
def safe_divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        return None
    finally:
        print("attempted division")

Catch specific exception types rather than a bare `except:`, and raise your own with `raise ValueError("message")`. Custom exceptions subclass `Exception`:

python
class InsufficientFunds(Exception):
    pass

Check your understanding

  1. 1. When does the `finally` block run?

  2. 2. Why avoid a bare `except:`?

  3. 3. How do you define a custom exception?