Exceptions

Try ... except

try:
    suite
[except [exception [, value]:
    suite]+
[else:
    suite]

• If no exception is raised, the "else" suite is run immediately after the "try" suite (unless the "try" suite exits with a return, break, or continue statement).
• Can specify a tuple of exceptions: except (KeyError, NameError)

Try ... finally

try:
    suite
finally:
    suite

• The "finally" suite is guaranteed to be run immediately after the "try" suite.
• If the "try" suite raised an exception, the "finally" suite will re-raise it.

Raise statement

raise exceptionInstance   # Use an existing exception instance (object)

raise exceptionClass [,value [, traceback-object]]   # Create new exception instance

raise

• A raise statement without arguments re-raises the last exception raised in the current function.

Assert statement

assert expr [, message]

• If the expression evaluates to false, an AssertionError exception is raised.
• Assertions are disabled if __debug__ is 0.