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"""Event loop integration for the ZeroMQ-based kernels."""
# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.
import os
import platform
import sys
from functools import partial
import zmq
from packaging.version import Version as V
from traitlets.config.application import Application
def _use_appnope():
"""Should we use appnope for dealing with OS X app nap?
Checks if we are on OS X 10.9 or greater.
"""
return sys.platform == "darwin" and V(platform.mac_ver()[0]) >= V("10.9")
# mapping of keys to loop functions
loop_map = {
"inline": None,
"nbagg": None,
"webagg": None,
"notebook": None,
"ipympl": None,
"widget": None,
None: None,
}
def register_integration(*toolkitnames):
"""Decorator to register an event loop to integrate with the IPython kernel
The decorator takes names to register the event loop as for the %gui magic.
You can provide alternative names for the same toolkit.
The decorated function should take a single argument, the IPython kernel
instance, arrange for the event loop to call ``kernel.do_one_iteration()``
at least every ``kernel._poll_interval`` seconds, and start the event loop.
:mod:`ipykernel.eventloops` provides and registers such functions
for a few common event loops.
"""
def decorator(func):
"""Integration registration decorator."""
for name in toolkitnames:
loop_map[name] = func
func.exit_hook = lambda kernel: None # noqa: ARG005
def exit_decorator(exit_func):
"""@func.exit is now a decorator
to register a function to be called on exit
"""
func.exit_hook = exit_func
return exit_func
func.exit = exit_decorator
return func
return decorator
def _notify_stream_qt(kernel):
import operator
from functools import lru_cache
from IPython.external.qt_for_kernel import QtCore
try:
from IPython.external.qt_for_kernel import enum_helper
except ImportError:
@lru_cache(None)
def enum_helper(name):
return operator.attrgetter(name.rpartition(".")[0])(sys.modules[QtCore.__package__])
def exit_loop():
"""fall back to main loop"""
kernel._qt_notifier.setEnabled(False)
kernel.app.qt_event_loop.quit()
def process_stream_events():
"""fall back to main loop when there's a socket event"""
# call flush to ensure that the stream doesn't lose events
# due to our consuming of the edge-triggered FD
# flush returns the number of events consumed.
# if there were any, wake it up
if kernel.shell_stream.flush(limit=1):
exit_loop()
if not hasattr(kernel, "_qt_notifier"):
fd = kernel.shell_stream.getsockopt(zmq.FD)
kernel._qt_notifier = QtCore.QSocketNotifier(
fd, enum_helper("QtCore.QSocketNotifier.Type").Read, kernel.app.qt_event_loop
)
kernel._qt_notifier.activated.connect(process_stream_events)
else:
kernel._qt_notifier.setEnabled(True)
# allow for scheduling exits from the loop in case a timeout needs to
# be set from the kernel level
def _schedule_exit(delay):
"""schedule fall back to main loop in [delay] seconds"""
# The signatures of QtCore.QTimer.singleShot are inconsistent between PySide and PyQt
# if setting the TimerType, so we create a timer explicitly and store it
# to avoid a memory leak.
# PreciseTimer is needed so we exit after _at least_ the specified delay, not within 5% of it
if not hasattr(kernel, "_qt_timer"):
kernel._qt_timer = QtCore.QTimer(kernel.app)
kernel._qt_timer.setSingleShot(True)
kernel._qt_timer.setTimerType(enum_helper("QtCore.Qt.TimerType").PreciseTimer)
kernel._qt_timer.timeout.connect(exit_loop)
kernel._qt_timer.start(int(1000 * delay))
loop_qt._schedule_exit = _schedule_exit
# there may already be unprocessed events waiting.
# these events will not wake zmq's edge-triggered FD
# since edge-triggered notification only occurs on new i/o activity.
# process all the waiting events immediately
# so we start in a clean state ensuring that any new i/o events will notify.
# schedule first call on the eventloop as soon as it's running,
# so we don't block here processing events
QtCore.QTimer.singleShot(0, process_stream_events)
@register_integration("qt", "qt5", "qt6")
def loop_qt(kernel):
"""Event loop for all supported versions of Qt."""
_notify_stream_qt(kernel) # install hook to stop event loop.
# Start the event loop.
kernel.app._in_event_loop = True
# `exec` blocks until there's ZMQ activity.
el = kernel.app.qt_event_loop # for brevity
el.exec() if hasattr(el, "exec") else el.exec_()
kernel.app._in_event_loop = False
# NOTE: To be removed in version 7
loop_qt5 = loop_qt
# exit and watch are the same for qt 4 and 5
@loop_qt.exit
def loop_qt_exit(kernel):
kernel.app.exit()
def _loop_wx(app):
"""Inner-loop for running the Wx eventloop
Pulled from guisupport.start_event_loop in IPython < 5.2,
since IPython 5.2 only checks `get_ipython().active_eventloop` is defined,
rather than if the eventloop is actually running.
"""
app._in_event_loop = True
app.MainLoop()
app._in_event_loop = False
@register_integration("wx")
def loop_wx(kernel):
"""Start a kernel with wx event loop support."""
import wx
# Wx uses milliseconds
poll_interval = int(1000 * kernel._poll_interval)
def wake():
"""wake from wx"""
if kernel.shell_stream.flush(limit=1):
kernel.app.ExitMainLoop()
return
# We have to put the wx.Timer in a wx.Frame for it to fire properly.
# We make the Frame hidden when we create it in the main app below.
class TimerFrame(wx.Frame): # type:ignore[misc]
def __init__(self, func):
wx.Frame.__init__(self, None, -1)
self.timer = wx.Timer(self)
# Units for the timer are in milliseconds
self.timer.Start(poll_interval)
self.Bind(wx.EVT_TIMER, self.on_timer)
self.func = func
def on_timer(self, event):
self.func()
# We need a custom wx.App to create our Frame subclass that has the
# wx.Timer to defer back to the tornado event loop.
class IPWxApp(wx.App): # type:ignore[misc]
def OnInit(self):
self.frame = TimerFrame(wake)
self.frame.Show(False)
return True
# The redirect=False here makes sure that wx doesn't replace
# sys.stdout/stderr with its own classes.
if not (getattr(kernel, "app", None) and isinstance(kernel.app, wx.App)):
kernel.app = IPWxApp(redirect=False)
# The import of wx on Linux sets the handler for signal.SIGINT
# to 0. This is a bug in wx or gtk. We fix by just setting it
# back to the Python default.
import signal
if not callable(signal.getsignal(signal.SIGINT)):
signal.signal(signal.SIGINT, signal.default_int_handler)
_loop_wx(kernel.app)
@loop_wx.exit
def loop_wx_exit(kernel):
"""Exit the wx loop."""
import wx
wx.Exit()
@register_integration("tk")
def loop_tk(kernel):
"""Start a kernel with the Tk event loop."""
from tkinter import READABLE, Tk
app = Tk()
# Capability detection:
# per https://docs.python.org/3/library/tkinter.html#file-handlers
# file handlers are not available on Windows
if hasattr(app, "createfilehandler"):
# A basic wrapper for structural similarity with the Windows version
class BasicAppWrapper:
def __init__(self, app):
self.app = app
self.app.withdraw()
def exit_loop():
"""fall back to main loop"""
app.tk.deletefilehandler(kernel.shell_stream.getsockopt(zmq.FD))
app.quit()
app.destroy()
del kernel.app_wrapper
def process_stream_events(*a, **kw):
"""fall back to main loop when there's a socket event"""
if kernel.shell_stream.flush(limit=1):
exit_loop()
# allow for scheduling exits from the loop in case a timeout needs to
# be set from the kernel level
def _schedule_exit(delay):
"""schedule fall back to main loop in [delay] seconds"""
app.after(int(1000 * delay), exit_loop)
loop_tk._schedule_exit = _schedule_exit
# For Tkinter, we create a Tk object and call its withdraw method.
kernel.app_wrapper = BasicAppWrapper(app)
app.tk.createfilehandler(
kernel.shell_stream.getsockopt(zmq.FD), READABLE, process_stream_events
)
# schedule initial call after start
app.after(0, process_stream_events)
app.mainloop()
else:
import asyncio
import nest_asyncio
nest_asyncio.apply()
doi = kernel.do_one_iteration
# Tk uses milliseconds
poll_interval = int(1000 * kernel._poll_interval)
class TimedAppWrapper:
def __init__(self, app, func):
self.app = app
self.app.withdraw()
self.func = func
def on_timer(self):
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(self.func())
except Exception:
kernel.log.exception("Error in message handler")
self.app.after(poll_interval, self.on_timer)
def start(self):
self.on_timer() # Call it once to get things going.
self.app.mainloop()
kernel.app_wrapper = TimedAppWrapper(app, doi)
kernel.app_wrapper.start()
@loop_tk.exit
def loop_tk_exit(kernel):
"""Exit the tk loop."""
try:
kernel.app_wrapper.app.destroy()
del kernel.app_wrapper
except (RuntimeError, AttributeError):
pass
@register_integration("gtk")
def loop_gtk(kernel):
"""Start the kernel, coordinating with the GTK event loop"""
from .gui.gtkembed import GTKEmbed
gtk_kernel = GTKEmbed(kernel)
gtk_kernel.start()
kernel._gtk = gtk_kernel
@loop_gtk.exit
def loop_gtk_exit(kernel):
"""Exit the gtk loop."""
kernel._gtk.stop()
@register_integration("gtk3")
def loop_gtk3(kernel):
"""Start the kernel, coordinating with the GTK event loop"""
from .gui.gtk3embed import GTKEmbed
gtk_kernel = GTKEmbed(kernel)
gtk_kernel.start()
kernel._gtk = gtk_kernel
@loop_gtk3.exit
def loop_gtk3_exit(kernel):
"""Exit the gtk3 loop."""
kernel._gtk.stop()
@register_integration("osx")
def loop_cocoa(kernel):
"""Start the kernel, coordinating with the Cocoa CFRunLoop event loop
via the matplotlib MacOSX backend.
"""
from ._eventloop_macos import mainloop, stop
real_excepthook = sys.excepthook
def handle_int(etype, value, tb):
"""don't let KeyboardInterrupts look like crashes"""
# wake the eventloop when we get a signal
stop()
if etype is KeyboardInterrupt:
print("KeyboardInterrupt caught in CFRunLoop", file=sys.__stdout__)
else:
real_excepthook(etype, value, tb)
while not kernel.shell.exit_now:
try:
# double nested try/except, to properly catch KeyboardInterrupt
# due to pyzmq Issue #130
try:
# don't let interrupts during mainloop invoke crash_handler:
sys.excepthook = handle_int
mainloop(kernel._poll_interval)
if kernel.shell_stream.flush(limit=1):
# events to process, return control to kernel
return
except BaseException:
raise
except KeyboardInterrupt:
# Ctrl-C shouldn't crash the kernel
print("KeyboardInterrupt caught in kernel", file=sys.__stdout__)
finally:
# ensure excepthook is restored
sys.excepthook = real_excepthook
@loop_cocoa.exit
def loop_cocoa_exit(kernel):
"""Exit the cocoa loop."""
from ._eventloop_macos import stop
stop()
@register_integration("asyncio")
def loop_asyncio(kernel):
"""Start a kernel with asyncio event loop support."""
import asyncio
loop = asyncio.get_event_loop()
# loop is already running (e.g. tornado 5), nothing left to do
if loop.is_running():
return
if loop.is_closed():
# main loop is closed, create a new one
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
loop._should_close = False # type:ignore[attr-defined]
# pause eventloop when there's an event on a zmq socket
def process_stream_events(stream):
"""fall back to main loop when there's a socket event"""
if stream.flush(limit=1):
loop.stop()
notifier = partial(process_stream_events, kernel.shell_stream)
loop.add_reader(kernel.shell_stream.getsockopt(zmq.FD), notifier)
loop.call_soon(notifier)
while True:
error = None
try:
loop.run_forever()
except KeyboardInterrupt:
continue
except Exception as e:
error = e
if loop._should_close: # type:ignore[attr-defined]
loop.close()
if error is not None:
raise error
break
@loop_asyncio.exit
def loop_asyncio_exit(kernel):
"""Exit hook for asyncio"""
import asyncio
loop = asyncio.get_event_loop()
async def close_loop():
if hasattr(loop, "shutdown_asyncgens"):
yield loop.shutdown_asyncgens()
loop._should_close = True # type:ignore[attr-defined]
loop.stop()
if loop.is_running():
close_loop()
elif not loop.is_closed():
loop.run_until_complete(close_loop) # type:ignore[arg-type]
loop.close()
def set_qt_api_env_from_gui(gui):
"""
Sets the QT_API environment variable by trying to import PyQtx or PySidex.
The user can generically request `qt` or a specific Qt version, e.g. `qt6`.
For a generic Qt request, we let the mechanism in IPython choose the best
available version by leaving the `QT_API` environment variable blank.
For specific versions, we check to see whether the PyQt or PySide
implementations are present and set `QT_API` accordingly to indicate to
IPython which version we want. If neither implementation is present, we
leave the environment variable set so IPython will generate a helpful error
message.
Notes
-----
- If the environment variable is already set, it will be used unchanged,
regardless of what the user requested.
"""
qt_api = os.environ.get("QT_API", None)
from IPython.external.qt_loaders import (
QT_API_PYQT5,
QT_API_PYQT6,
QT_API_PYSIDE2,
QT_API_PYSIDE6,
loaded_api,
)
loaded = loaded_api()
qt_env2gui = {
QT_API_PYSIDE2: "qt5",
QT_API_PYQT5: "qt5",
QT_API_PYSIDE6: "qt6",
QT_API_PYQT6: "qt6",
}
if loaded is not None and gui != "qt" and qt_env2gui[loaded] != gui:
print(f"Cannot switch Qt versions for this session; you must use {qt_env2gui[loaded]}.")
return
if qt_api is not None and gui != "qt":
if qt_env2gui[qt_api] != gui:
print(
f'Request for "{gui}" will be ignored because `QT_API` '
f'environment variable is set to "{qt_api}"'
)
return
else:
if gui == "qt5":
try:
import PyQt5 # noqa: F401
os.environ["QT_API"] = "pyqt5"
except ImportError:
try:
import PySide2 # noqa: F401
os.environ["QT_API"] = "pyside2"
except ImportError:
os.environ["QT_API"] = "pyqt5"
elif gui == "qt6":
try:
import PyQt6 # noqa: F401
os.environ["QT_API"] = "pyqt6"
except ImportError:
try:
import PySide6 # noqa: F401
os.environ["QT_API"] = "pyside6"
except ImportError:
os.environ["QT_API"] = "pyqt6"
elif gui == "qt":
# Don't set QT_API; let IPython logic choose the version.
if "QT_API" in os.environ:
del os.environ["QT_API"]
else:
print(f'Unrecognized Qt version: {gui}. Should be "qt5", "qt6", or "qt".')
return
# Do the actual import now that the environment variable is set to make sure it works.
try:
pass
except Exception as e:
# Clear the environment variable for the next attempt.
if "QT_API" in os.environ:
del os.environ["QT_API"]
print(f"QT_API couldn't be set due to error {e}")
return
def make_qt_app_for_kernel(gui, kernel):
"""Sets the `QT_API` environment variable if it isn't already set."""
if hasattr(kernel, "app"):
# Kernel is already running a Qt event loop, so there's no need to
# create another app for it.
return
set_qt_api_env_from_gui(gui)
# This import is guaranteed to work now:
from IPython.external.qt_for_kernel import QtCore
from IPython.lib.guisupport import get_app_qt4
kernel.app = get_app_qt4([" "])
kernel.app.qt_event_loop = QtCore.QEventLoop(kernel.app)
def enable_gui(gui, kernel=None):
"""Enable integration with a given GUI"""
if gui not in loop_map:
e = f"Invalid GUI request {gui!r}, valid ones are:{loop_map.keys()}"
raise ValueError(e)
if kernel is None:
if Application.initialized():
kernel = getattr(Application.instance(), "kernel", None)
if kernel is None:
msg = (
"You didn't specify a kernel,"
" and no IPython Application with a kernel appears to be running."
)
raise RuntimeError(msg)
if gui is None:
# User wants to turn off integration; clear any evidence if Qt was the last one.
if hasattr(kernel, "app"):
delattr(kernel, "app")
if hasattr(kernel, "_qt_notifier"):
delattr(kernel, "_qt_notifier")
if hasattr(kernel, "_qt_timer"):
delattr(kernel, "_qt_timer")
else:
if gui.startswith("qt"):
# Prepare the kernel here so any exceptions are displayed in the client.
make_qt_app_for_kernel(gui, kernel)
loop = loop_map[gui]
if (
loop and kernel.eventloop is not None and kernel.eventloop is not loop # type:ignore[unreachable]
):
msg = "Cannot activate multiple GUI eventloops" # type:ignore[unreachable]
raise RuntimeError(msg)
kernel.eventloop = loop
# We set `eventloop`; the function the user chose is executed in `Kernel.enter_eventloop`, thus
# any exceptions raised during the event loop will not be shown in the client.
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