python内置了许多异常类型，他们的继承关系如下：
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BaseException

 +-- SystemExit

 +-- KeyboardInterrupt

 +-- GeneratorExit

 +-- Exception

      +-- StopIteration

      +-- StandardError

      |    +-- BufferError

      |    +-- ArithmeticError

      |    |    +-- FloatingPointError

      |    |    +-- OverflowError

      |    |    +-- ZeroDivisionError

      |    +-- AssertionError

      |    +-- AttributeError

      |    +-- EnvironmentError

      |    |    +-- IOError

      |    |    +-- OSError

      |    |         +-- WindowsError (Windows)

      |    |         +-- VMSError (VMS)

      |    +-- EOFError

      |    +-- ImportError

      |    +-- LookupError

      |    |    +-- IndexError

      |    |    +-- KeyError

      |    +-- MemoryError

      |    +-- NameError

      |    |    +-- UnboundLocalError

      |    +-- ReferenceError

      |    +-- RuntimeError

      |    |    +-- NotImplementedError

      |    +-- SyntaxError

      |    |    +-- IndentationError

      |    |         +-- TabError

      |    +-- SystemError

      |    +-- TypeError

      |    +-- ValueError

      |         +-- UnicodeError

      |              +-- UnicodeDecodeError

      |              +-- UnicodeEncodeError

      |              +-- UnicodeTranslateError

      +-- Warning

           +-- DeprecationWarning

           +-- PendingDeprecationWarning

           +-- RuntimeWarning

           +-- SyntaxWarning

           +-- UserWarning

           +-- FutureWarning

	   +-- ImportWarning

	   +-- UnicodeWarning

	   +-- BytesWarning
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一般在自己编写程序的时候需要注意的就是TypeError、ValueError
在编写继承关系的类时，定义基类的需要被子类覆盖的方法时要注意NotImplementedError

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原文链接：https://docs.python.org/2/library/exceptions.html