gistfile1.py

# pylint: disable=too-few-public-methods, redefined-builtin, invalid-name
class Torpor(object):
    """
    Announce that we're about to do something, then do it,
    then say we're done.

    Usage: ::

        with Torpor("doing a slow thing"):
            some_slow_thing

    Output (1): ::

        doing a slow thing...

    Output (2a): ::

        doing a slow thing... done

    Output (2b): ::

        doing a slow thing... ERROR
        <stack trace>
    """
    def __init__(self, msg, sameline=True, file=sys.stderr):
        self._msg = msg
        self._file = file
        self._sameline = sameline

    def __enter__(self):
        if self._sameline:
            print(self._msg, end="... ", file=self._file)
        else:
            print("[start]", self._msg, file=self._file)

    def __exit__(self, type, value, tb):
        if tb is None:
            done = "done" if self._sameline else "[end] " + self._msg
            print(done, file=self._file)
        else:
            oops = "ERROR!" if self._sameline else "ERROR! " + self._msg
            print(oops, file=self._file)
            traceback.print_exception(type, value, tb)
            sys.exit(1)
# pylint: enable=too-few-public-methods, redefined-builtin, invalid-name