10. Exceptions¶

10.1 Overview¶

When there’s an error in a Python code, the output includes a Traceback. This often helps you identify and trace the error.
To catch an error, use try blocks.

try:
    x = int('foo')
except ValueError:
    print('I caught a ValueError')
else:
    print('good job!') # only executed if there is no error

ValueError is just one type of error.
Other errors include ZeroDivisionError
If error type is not known, simply use except: without specifying the type of error.
Python has a rich and complete system for handling exceptions.

10.2 Reporting¶

Think of exceptions as a way to describe runtime errors.
Generate an exception using raise:

# initialize parameters
if numargs < 1:
    raise TypeError(f'expected at least 1 argument, got {numargs}')

Such exceptions can also be caught in a try block.

9. Classes 11. String Objects