upstream/ipython Files · IPython/utils/nested_context.py

Prevent qtconsole frontend freeze on lots of output....

Prevent qtconsole frontend freeze on lots of output. The output from the kernel is now clipped to last `buffer_size` before displaying and a timer is used to flush the pending output text instead of attempting to display text on every stream output from kernel. The timer interval is adjusted based on actual time taken to append a screenful of text to widget. This throttles the widget repaints and avoids choking the Qt event loop leaving time to handle other Qt events. Test cases: In [1]: for i in xrange(1000000): print i In [2]: range(100000) Without this commit the first input causes the qtconsole frontend to freeze, not responding to `Ctrl+C`.

Thomas Kluyver - - Load All Authors

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             nested_context.py
        
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      """Backwards compatibility - we use contextlib.nested to support Python 2.6,

      but it's removed in Python 3.2."""

      # TODO : Remove this once we drop support for Python 2.6, and use

      # "with a, b:" instead.

      import sys

      from contextlib import contextmanager

      @contextmanager

      def nested(*managers):

          """Combine multiple context managers into a single nested context manager.

         This function has been deprecated in favour of the multiple manager form

         of the with statement.

         The one advantage of this function over the multiple manager form of the

         with statement is that argument unpacking allows it to be

         used with a variable number of context managers as follows::

            with nested(*managers):

                do_something()

          """

          exits = []

          vars = []

          exc = (None, None, None)

          try:

              for mgr in managers:

                  exit = mgr.__exit__

                  enter = mgr.__enter__

                  vars.append(enter())

                  exits.append(exit)

              yield vars

          except:

              exc = sys.exc_info()

          finally:

              while exits:

                  exit = exits.pop()

                  try:

                      if exit(*exc):

                          exc = (None, None, None)

                  except:

                      exc = sys.exc_info()

              if exc != (None, None, None):

                  # Don't rely on sys.exc_info() still containing

                  # the right information. Another exception may

                  # have been raised and caught by an exit method

                  raise exc[0], exc[1], exc[2]

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				"""Backwards compatibility - we use contextlib.nested to support Python 2.6,
				but it's removed in Python 3.2."""

				# TODO : Remove this once we drop support for Python 2.6, and use
				# "with a, b:" instead.

				import sys

				from contextlib import contextmanager

				@contextmanager
				def nested(*managers):
				"""Combine multiple context managers into a single nested context manager.

				This function has been deprecated in favour of the multiple manager form
				of the with statement.

				The one advantage of this function over the multiple manager form of the
				with statement is that argument unpacking allows it to be
				used with a variable number of context managers as follows::

				with nested(*managers):
				do_something()

				"""
				exits = []
				vars = []
				exc = (None, None, None)
				try:
				for mgr in managers:
				exit = mgr.__exit__
				enter = mgr.__enter__
				vars.append(enter())
				exits.append(exit)
				yield vars
				except:
				exc = sys.exc_info()
				finally:
				while exits:
				exit = exits.pop()
				try:
				if exit(*exc):
				exc = (None, None, None)
				except:
				exc = sys.exc_info()
				if exc != (None, None, None):
				# Don't rely on sys.exc_info() still containing
				# the right information. Another exception may
				# have been raised and caught by an exit method
				raise exc[0], exc[1], exc[2]