Lesson 9
No Object is an Island
Chapter 9: Exception handling
Built-in Exceptions
Below is the a list of all Python built-in exceptions (reproduced from the official documentation).
All built-in exceptions are special instances of BaseException, and is arranged in a class hierarchy. So Exception is a special kind of BaseException, ZeroDivisionError is a special kind of ArithmeticError, etc. We will discuss more about class hierarchy in the next lesson.
You may have already encountered some of these exceptions. How many of these classes do you recognise?
BaseException
+-- SystemExit
+-- KeyboardInterrupt
+-- GeneratorExit
+-- Exception
+-- StopIteration
+-- StopAsyncIteration
+-- ArithmeticError
| +-- FloatingPointError
| +-- OverflowError
| +-- ZeroDivisionError
+-- AssertionError
+-- AttributeError
+-- BufferError
+-- EOFError
+-- ImportError
| +-- ModuleNotFoundError
+-- LookupError
| +-- IndexError
| +-- KeyError
+-- MemoryError
+-- NameError
| +-- UnboundLocalError
+-- OSError
| +-- BlockingIOError
| +-- ChildProcessError
| +-- ConnectionError
| | +-- BrokenPipeError
| | +-- ConnectionAbortedError
| | +-- ConnectionRefusedError
| | +-- ConnectionResetError
| +-- FileExistsError
| +-- FileNotFoundError
| +-- InterruptedError
| +-- IsADirectoryError
| +-- NotADirectoryError
| +-- PermissionError
| +-- ProcessLookupError
| +-- TimeoutError
+-- ReferenceError
+-- RuntimeError
| +-- NotImplementedError
| +-- RecursionError
+-- SyntaxError
| +-- IndentationError
| +-- TabError
+-- SystemError
+-- TypeError
+-- ValueError
| +-- UnicodeError
| +-- UnicodeDecodeError
| +-- UnicodeEncodeError
| +-- UnicodeTranslateError
+-- Warning
+-- DeprecationWarning
+-- PendingDeprecationWarning
+-- RuntimeWarning
+-- SyntaxWarning
+-- UserWarning
+-- FutureWarning
+-- ImportWarning
+-- UnicodeWarning
+-- BytesWarning
+-- ResourceWarning
Try skimming through the documentation for more details about these Exceptions. Some that you might often encounter often include ModuleNotFoundError, TypeError, ValueError, IndexError (e.g. trying to access a list element that is beyond the size of the list), KeyError (e.g. accessing a dictionary element with an invalid key), FileNotFoundError, and one of the ArithmeticErrors. Understanding what these exceptions represent will enable you to debug your code better in the future.
You are also encouraged to choose a semantically suitable Exception if you are raising your own exceptions.