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The scope for exception handlers starts with a marker clause (try or the language's block starter such as begin) and ends in the start of the first handler clause (catch, except, rescue). Several handler clauses can follow, and each can specify which exception types it handles and what name it uses for the exception object.
C does not provide direct support to exception handling: it is the programmer's responsibility to prevent errors in the first place and test return values from the functions.
Common exceptions include an invalid argument (e.g. value is outside of the domain of a function), [5] an unavailable resource (like a missing file, [6] a network drive error, [7] or out-of-memory errors [8]), or that the routine has detected a normal condition that requires special handling, e.g., attention, end of file. [9]
The try statement, which allows exceptions raised in its attached code block to be caught and handled by except clauses (or new syntax except* in Python 3.11 for exception groups [97]); it also ensures that clean-up code in a finally block is always run regardless of how the block exits
Languages without a return statement, such as standard Pascal don't have this problem. Some languages, such as C++ and Python, employ concepts which allow actions to be performed automatically upon return (or exception throw) which mitigates some of these issues – these are often known as "try/finally" or similar.
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
Exception swallowing can also happen if the exception is handled and rethrown as a different exception, discarding the original exception and all its context. In this C# example, all exceptions are caught regardless of type, and a new generic exception is thrown, keeping only the message of the original exception.
A method returns to the code that invoked it when it completes all the statements in the method, reaches a return statement, or throws an exception, whichever occurs first. You declare a method's return type in its method declaration. Within the body of the method, you use the return statement to return the value.