Learn Exception Handling in Python with try and except block, catch multiple exceptions, else and finally clause, raise an exception, user-defined exceptions and much more. Assertions in Python. An expression is tested, and if the result comes up false, an exception is raised. In Python 2.4 and before, any (classic) class can be raised as an exception. You can learn more about why this is a good idea in this tutorial. Instead, you’ll want to refer to specific exception classes you want to catch and handle. In Python, users can define custom exceptions by creating a new class. The easiest way to think of an assertion is to liken it to a raise-if statement (or to be more accurate, a raise-if-not statement). Set the traceback associated with the exception …

This exception class has to be derived, either directly or indirectly, from the built-in Exception class. Most of the built-in exceptions are also derived from this class. Warning: Catching Exception hides all errors…even those which are completely unexpected.

Abstract. An assertion is a sanity-check that you can turn on or turn off when you are done with your testing of the program.

Exception Objects¶ PyObject* PyException_GetTraceback (PyObject *ex) ¶ Return value: New reference. This is why you should avoid bare except clauses in your Python programs. This is a problem as it prevents any guarantees from being made about the interface of exceptions.

The plan for 2.5 was to allow new-style classes, but this makes the problem worse -- it would mean any class (or instance) can be raised! Return the traceback associated with the exception as a new reference, as accessible from Python through __traceback__.If there is no traceback associated, this returns NULL.. int PyException_SetTraceback (PyObject *ex, PyObject *tb) ¶.