如果发生异常，那么通过调用sys.exc_info()函数，可以返回包含3个元素的元组。 第一个元素就是引发异常类，而第二个是实际引发的实例，第三个元素traceback对象，代表异常最初发生时调用的堆栈。如果一切正常，那么会返回3个None。
Python的Builtins模块中定义的Exception |Exception Name|Description| |BaseException|Root class for all exceptions| | SystemExit|Request termination of Python interpreter| |KeyboardInterrupt|User interrupted execution (usually by pressing Ctrl+C)| |Exception|Root class for regular exceptions| | StopIteration|Iteration has no further values| | GeneratorExit|Exception sent to generator to tell it to quit| | SystemExit|Request termination of Python interpreter| | StandardError|Base class for all standard built-in exceptions| | ArithmeticError|Base class for all numeric calculation errors| | FloatingPointError|Error in floating point calculation| | OverflowError|Calculation exceeded maximum limit for numerical type| | ZeroDivisionError|Division (or modulus) by zero error (all numeric types)| | AssertionError|Failure of assert statement| | AttributeError|No such object attribute| | EOFError|End-of-file marker reached without input from built-in| | EnvironmentError|Base class for operating system environment errors| | IOError|Failure of input/output operation| | OSError|Operating system error| | WindowsError|MS Windows system call failure| | ImportError|Failure to import module or object| | KeyboardInterrupt|User interrupted execution (usually by pressing Ctrl+C)| | LookupError|Base class for invalid data lookup errors| | IndexError|No such index in sequence| | KeyError|No such key in mapping| | MemoryError|Out-of-memory error (non-fatal to Python interpreter)| | NameError|Undeclared/uninitialized object(non-attribute)| | UnboundLocalError|Access of an uninitialized local variable| | ReferenceError|Weak reference tried to access a garbage collected object| | RuntimeError|Generic default error during execution| | NotImplementedError|Unimplemented method| | SyntaxError|Error in Python syntax| | IndentationError|Improper indentation| | TabErrorg|Improper mixture of TABs and spaces| | SystemError|Generic interpreter system error| | TypeError|Invalid operation for type| | ValueError|Invalid argument given| | UnicodeError|Unicode-related error| | UnicodeDecodeError|Unicode error during decoding| | UnicodeEncodeError|Unicode error during encoding| | UnicodeTranslate Error|Unicode error during translation| | Warning|Root class for all warnings| | DeprecationWarning|Warning about deprecated features| | FutureWarning|Warning about constructs that will change semantically in the future| | OverflowWarning|Old warning for auto-long upgrade| | PendingDeprecation Warning|Warning about features that will be deprecated in the future| | RuntimeWarning|Warning about dubious runtime behavior| | SyntaxWarning|Warning about dubious syntax| | UserWarning|Warning generated by user code|下面关于Python的文章您也可能喜欢，不妨看看：
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