59 lines
2.2 KiB
Plaintext
59 lines
2.2 KiB
Plaintext
https://docs.python.org/3/library/exceptions.html#SystemExit[``++SystemExit++``] is raised when https://docs.python.org/3/library/sys.html#sys.exit[``++sys.exit()++``] is called. https://docs.python.org/3/library/exceptions.html#KeyboardInterrupt[``++KeyboardInterrupt++``] is raised when the user asks the program to stop by pressing interrupt keys. Both exceptions are expected to propagate up until the application stops.
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In order to avoid catching ``++SystemExit++`` and ``++KeyboardInterrupt++`` by mistake https://www.python.org/dev/peps/pep-0352/#exception-hierarchy[PEP-352] created the root class ``++BaseException++`` from which ``++SystemExit++``, ``++KeyboardInterrupt++`` and ``++Exception++`` derive. Thus developers can use ``++except Exception:++`` without preventing the software from stopping.
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The ``++GeneratorExit++`` class also derives from ``++BaseException++`` as it is not really an error and is not supposed to be caught by user code.
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As said in https://docs.python.org/3/library/exceptions.html#BaseException[Python's documentation], user-defined exceptions are not supposed to inherit directly from ``++BaseException++``. They should instead inherit from ``++Exception++`` or one of its subclasses.
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This rule raises an issue when a class derives from one of the following exception classes: ``++BaseException++``, ``++KeyboardInterrupt++``, ``++SystemExit++`` or ``++GeneratorExit++``.
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== Noncompliant Code Example
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[source,python]
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----
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class MyException(BaseException): # Noncompliant
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pass
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class MyException(GeneratorExit): # Noncompliant
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pass
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class MyException(KeyboardInterrupt): # Noncompliant
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pass
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class MyException(SystemExit): # Noncompliant
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pass
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----
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== Compliant Solution
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[source,python]
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----
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class MyException(Exception):
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pass
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----
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== See
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* PEP 352 – https://www.python.org/dev/peps/pep-0352/#exception-hierarchy-changes[Required Superclass for Exceptions]
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* Python Documentation - https://docs.python.org/3/library/exceptions.html#BaseException[BaseException class]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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include::message.adoc[]
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include::highlighting.adoc[]
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endif::env-github,rspecator-view[]
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