upstream/ipython Files · IPython/terminal/pt_inputhooks/pyglet.py

Swallow potential exceptions from showtraceback()...

Swallow potential exceptions from showtraceback() The nbgrader project is aware of a form of cheating where students disrupt `InteractiveShell.showtraceback` in hopes of hiding exceptions to avoid losing points. They have implemented a solution to prevent this cheating from working on the client side, and have some tests to demonstrate this technique: https://github.com/jupyter/nbgrader/blob/main/nbgrader/tests/apps/files/submitted-cheat-attempt.ipynb https://github.com/jupyter/nbgrader/blob/main/nbgrader/tests/apps/files/submitted-cheat-attempt-alternative.ipynb In essence, these attacks import the interactive shell and erase the traceback handler so that their failing tests won't report failures. import IPython.core.interactiveshell IPython.core.interactiveshell.InteractiveShell.showtraceback = None The problem is that this causes an exception inside the kernel, leading to a stalled execution. The kernel has stopped working, but the client continues to wait for messages. So far, nbgrader's solution to this is to require a timeout value so the client can eventually decide it is done. This prevents allowing a value of `None` for `Execute.timeout` because this would cause a test case to infinitely hang. This commit addresses the problem by making `InteractiveShell._run_cell` a little more protective around it's call to `showtraceback()`. There is already a try/except block around running the cell. This commit adds a finally clause so that the method will _always_ return an `ExecutionResult`, even if a new exception is thrown within the except clause. For the record, the exception thrown is: TypeError: 'NoneType' object is not callable Accepting this change will allow nbgrader to update `nbgrader.preprocessors.Execute` to support a type of `Integer(allow_none=True)` as the parent `NotebookClient` intended. Discussion about this is ongoing in jupyter/nbgrader#1690.

Matthew R. Scott - - Load All Authors

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      """Enable pyglet to be used interactively with prompt_toolkit

      """

      import sys

      import time

      from timeit import default_timer as clock

      import pyglet

      # On linux only, window.flip() has a bug that causes an AttributeError on

      # window close.  For details, see:

      # http://groups.google.com/group/pyglet-users/browse_thread/thread/47c1aab9aa4a3d23/c22f9e819826799e?#c22f9e819826799e

      if sys.platform.startswith('linux'):

          def flip(window):

              try:

                  window.flip()

              except AttributeError:

                  pass

      else:

          def flip(window):

              window.flip()

      def inputhook(context):

          """Run the pyglet event loop by processing pending events only.

          This keeps processing pending events until stdin is ready.  After

          processing all pending events, a call to time.sleep is inserted.  This is

          needed, otherwise, CPU usage is at 100%.  This sleep time should be tuned

          though for best performance.

          """

          # We need to protect against a user pressing Control-C when IPython is

          # idle and this is running. We trap KeyboardInterrupt and pass.

          try:

              t = clock()

              while not context.input_is_ready():

                  pyglet.clock.tick()

                  for window in pyglet.app.windows:

                      window.switch_to()

                      window.dispatch_events()

                      window.dispatch_event('on_draw')

                      flip(window)

                  # We need to sleep at this point to keep the idle CPU load

                  # low.  However, if sleep to long, GUI response is poor.  As

                  # a compromise, we watch how often GUI events are being processed

                  # and switch between a short and long sleep time.  Here are some

                  # stats useful in helping to tune this.

                  # time    CPU load

                  # 0.001   13%

                  # 0.005   3%

                  # 0.01    1.5%

                  # 0.05    0.5%

                  used_time = clock() - t

                  if used_time > 10.0:

                      # print 'Sleep for 1 s'  # dbg

                      time.sleep(1.0)

                  elif used_time > 0.1:

                      # Few GUI events coming in, so we can sleep longer

                      # print 'Sleep for 0.05 s'  # dbg

                      time.sleep(0.05)

                  else:

                      # Many GUI events coming in, so sleep only very little

                      time.sleep(0.001)

          except KeyboardInterrupt:

              pass

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				"""Enable pyglet to be used interactively with prompt_toolkit
				"""

				import sys
				import time
				from timeit import default_timer as clock
				import pyglet

				# On linux only, window.flip() has a bug that causes an AttributeError on
				# window close. For details, see:
				# http://groups.google.com/group/pyglet-users/browse_thread/thread/47c1aab9aa4a3d23/c22f9e819826799e?#c22f9e819826799e

				if sys.platform.startswith('linux'):
				def flip(window):
				try:
				window.flip()
				except AttributeError:
				pass
				else:
				def flip(window):
				window.flip()


				def inputhook(context):
				"""Run the pyglet event loop by processing pending events only.

				This keeps processing pending events until stdin is ready. After
				processing all pending events, a call to time.sleep is inserted. This is
				needed, otherwise, CPU usage is at 100%. This sleep time should be tuned
				though for best performance.
				"""
				# We need to protect against a user pressing Control-C when IPython is
				# idle and this is running. We trap KeyboardInterrupt and pass.
				try:
				t = clock()
				while not context.input_is_ready():
				pyglet.clock.tick()
				for window in pyglet.app.windows:
				window.switch_to()
				window.dispatch_events()
				window.dispatch_event('on_draw')
				flip(window)

				# We need to sleep at this point to keep the idle CPU load
				# low. However, if sleep to long, GUI response is poor. As
				# a compromise, we watch how often GUI events are being processed
				# and switch between a short and long sleep time. Here are some
				# stats useful in helping to tune this.
				# time CPU load
				# 0.001 13%
				# 0.005 3%
				# 0.01 1.5%
				# 0.05 0.5%
				used_time = clock() - t
				if used_time > 10.0:
				# print 'Sleep for 1 s' # dbg
				time.sleep(1.0)
				elif used_time > 0.1:
				# Few GUI events coming in, so we can sleep longer
				# print 'Sleep for 0.05 s' # dbg
				time.sleep(0.05)
				else:
				# Many GUI events coming in, so sleep only very little
				time.sleep(0.001)
				except KeyboardInterrupt:
				pass