configure_traits 在 Spyder/Anaconda 中冻结控制台

Question

尝试 traitsui 文档中的第一个示例：

from traits.api import HasTraits, Str, Int
from traitsui.api import View, Item
import traitsui

class SimpleEmployee(HasTraits):
    first_name = Str
    last_name = Str
    department = Str
    employee_number = Str
    salary = Int

view1 = View(Item(name = 'first_name'),
             Item(name = 'last_name'),
             Item(name = 'department'))

sam = SimpleEmployee()
sam.configure_traits(view=view1)

使 Spyder IPython 控制台挂起，即使 UI window 已关闭。

MacOSX 10.14.6、Spyder 4.0.0、Python3.7.0、IPython7.10.2、traitsui 6.1.3

可能需要配置一些关于 UI 事件循环的东西，但是是什么以及如何配置？

Answer 1

Canopy IPython 控制台和 Spyder IPython 控制台的区别在于

app = QtGui.QApplication.instance()
print(app)

returns

<PyQt5.QtWidgets.QApplication at 0xXXXXXXXX>

两者都是，但是

is_event_loop_running_qt4(app)

returns True 在 Canopy IPython 终端和 False 在 Spyder IPython 终端。

有必要在 traits.qt4.view_application 中修补 view_application()，方法是注释掉开始新 ViewApplication 实例的行，具体取决于此测试。可以运行以下代码代替更改原始文件：

# -*- coding: utf-8 -*-

"""Avoid Spyder console to hang when using configure_traits()
"""

from IPython import get_ipython

from pyface.qt import QtCore, QtGui, qt_api
from pyface.util.guisupport import is_event_loop_running_qt4

from traitsui.api import toolkit
from traitsui.qt4.view_application import ViewApplication

KEEP_ALIVE_UIS = set()

def on_ui_destroyed(object, name, old, destroyed):
    """ Remove the UI object from KEEP_ALIVE_UIS.
    """
    assert name == 'destroyed'
    if destroyed:
        assert object in KEEP_ALIVE_UIS
        KEEP_ALIVE_UIS.remove(object)
        object.on_trait_change(on_ui_destroyed, 'destroyed', remove=True)

def _view_application(context, view, kind, handler, id, scrollable, args):
    """ Creates a stand-alone PyQt application to display a specified traits UI
        View.

    Parameters
    ----------
    context : object or dictionary
        A single object or a dictionary of string/object pairs, whose trait
        attributes are to be edited. If not specified, the current object is
        used.
    view : view object
        A View object that defines a user interface for editing trait attribute
        values.
    kind : string
        The type of user interface window to create. See the
        **traitsui.view.kind_trait** trait for values and
        their meanings. If *kind* is unspecified or None, the **kind**
        attribute of the View object is used.
    handler : Handler object
        A handler object used for event handling in the dialog box. If
        None, the default handler for Traits UI is used.
    scrollable : Boolean
        Indicates whether the dialog box should be scrollable. When set to
        True, scroll bars appear on the dialog box if it is not large enough
        to display all of the items in the view at one time.


    """
    if (kind == 'panel') or ((kind is None) and (view.kind == 'panel')):
        kind = 'modal'

    # !!!!!!! The following 4 lines commented out !!!!!!!!!!!
    # app = QtGui.QApplication.instance()
    # if app is None or not is_event_loop_running_qt4(app):
    #     return ViewApplication(context, view, kind, handler, id,
    #                            scrollable, args).ui.result
    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    ui = view.ui(context,
                 kind=kind,
                 handler=handler,
                 id=id,
                 scrollable=scrollable,
                 args=args)

    # If the UI has not been closed yet, we need to keep a reference to
    # it until it does close.
    if not ui.destroyed:
        KEEP_ALIVE_UIS.add(ui)
        ui.on_trait_change(on_ui_destroyed, 'destroyed')
    return ui.result

def view_application(self, context, view, kind=None, handler=None,
                     id='', scrollable=None, args=None):
    """ Creates a PyQt modal dialog user interface that
        runs as a complete application, using information from the
        specified View object.

    Parameters
    ----------
    context : object or dictionary
        A single object or a dictionary of string/object pairs, whose trait
        attributes are to be edited. If not specified, the current object is
        used.
    view : view or string
        A View object that defines a user interface for editing trait
        attribute values.
    kind : string
        The type of user interface window to create. See the
        **traitsui.view.kind_trait** trait for values and
        their meanings. If *kind* is unspecified or None, the **kind**
        attribute of the View object is used.
    handler : Handler object
        A handler object used for event handling in the dialog box. If
        None, the default handler for Traits UI is used.
    id : string
        A unique ID for persisting preferences about this user interface,
        such as size and position. If not specified, no user preferences
        are saved.
    scrollable : Boolean
        Indicates whether the dialog box should be scrollable. When set to
        True, scroll bars appear on the dialog box if it is not large enough
        to display all of the items in the view at one time.

    """
    return _view_application(context, view, kind, handler,
                                             id, scrollable, args)

from traitsui.qt4.toolkit import GUIToolkit

GUIToolkit.view_application = view_application

因此，该行为在 Spyder 和 Canopy IPython 控制台中都是正常的。请注意 configure_traits(kind='modal') 也可以。

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