interactiveshell.py 文件源码

def _get_exc_info(self, exc_tuple=None):
        """get exc_info from a given tuple, sys.exc_info() or sys.last_type etc.

        Ensures sys.last_type,value,traceback hold the exc_info we found,
        from whichever source.

        raises ValueError if none of these contain any information
        """
        if exc_tuple is None:
            etype, value, tb = sys.exc_info()
        else:
            etype, value, tb = exc_tuple

        if etype is None:
            if hasattr(sys, 'last_type'):
                etype, value, tb = sys.last_type, sys.last_value, \
                                   sys.last_traceback

        if etype is None:
            raise ValueError("No exception to find")

        # Now store the exception info in sys.last_type etc.
        # WARNING: these variables are somewhat deprecated and not
        # necessarily safe to use in a threaded environment, but tools
        # like pdb depend on their existence, so let's set them.  If we
        # find problems in the field, we'll need to revisit their use.
        sys.last_type = etype
        sys.last_value = value
        sys.last_traceback = tb

        return etype, value, tb