Question

尝试在http://traitlets.readthedocs.io/en/stable/using_traitlets.html#observe中重现该示例，但是使用窗口小部件作为类属性，行为会发生变化，并且不会在更改中发现

from ipywidgets import Label
from traitlets import HasTraits, Unicode, observe
class Foo(HasTraits):
    bar = Label()
    baz = Unicode()

    @observe('bar')
    def _observe_bar(self, change):
        print(change['old'])
        print(change['new'])

f = Foo()
f.bar = Label('hello')  # No printing

Answer 1

我从Sylvain Corlay（https://github.com/jupyter-widgets/ipywidgets/issues/2078）获得了ipywidgets repo的问题跟踪器的答案

您需要使用Instance特质类型。（Instance(Label)）

所以

from ipywidgets import Label
from traitlets import HasTraits, Unicode, observe, Instance
class Foo(HasTraits):
    bar = Instance(Label)
    baz = Unicode()

    @observe('bar')
    def _observe_bar(self, change):
        print(change['old'])
        print(change['new'])

f = Foo()
f.bar = Label('hello')  # No printing

使用来自ipywidgets的小部件的观察者模式

1 个答案: