Traiterror in ipywidgets 7.0.0b3 and 7.0.0b4

[DougRzz]

Hi,

When I upgrade to ipywidgets 7.0.0b3 I get the following error message in Jupyter (see below). I do not get this message in 7.0.0b2. The Jupyter cell had numerous ipywidgets including buttons, multi-select drop down widgets. I can try and isolate the issue and send an example if you need more information.

---

TraitError Traceback (most recent call last)
in ()
138 readout=True,
139 readout_format='i',
--> 140 slider_color='white'
141 )
142 def on_change(change):

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\ipywidgets\widgets\widget_int.py in init(self, value, min, max, step, **kwargs)
59 if step is not None:
60 kwargs['step'] = step
---> 61 super(cls, self).init(**kwargs)
62
63 init.doc = _bounded_int_doc_t

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\ipywidgets\widgets\widget_int.py in init(self, value, min, max, step, **kwargs)
91 if step is not None:
92 kwargs['step'] = step
---> 93 super(_BoundedInt, self).init(**kwargs)
94
95 @Validate('value')

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\ipywidgets\widgets\widget_int.py in init(self, value, **kwargs)
73 if value is not None:
74 kwargs['value'] = value
---> 75 super(_Int, self).init(**kwargs)
76
77

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\ipywidgets\widgets\widget.py in init(self, **kwargs)
367 """Public constructor"""
368 self._model_id = kwargs.pop('model_id', None)
--> 369 super(Widget, self).init(**kwargs)
370
371 Widget._call_widget_constructed(self)

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\traitlets\traitlets.py in init(self, *args, **kwargs)
995 for key, value in kwargs.items():
996 if self.has_trait(key):
--> 997 setattr(self, key, value)
998 else:
999 # passthrough args that don't set traits to super

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\traitlets\traitlets.py in set(self, obj, value)
583 raise TraitError('The "%s" trait is read-only.' % self.name)
584 else:
--> 585 self.set(obj, value)
586
587 def _validate(self, obj, value):

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\traitlets\traitlets.py in set(self, obj, value)
557
558 def set(self, obj, value):
--> 559 new_value = self._validate(obj, value)
560 try:
561 old_value = obj._trait_values[self.name]

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\traitlets\traitlets.py in _validate(self, obj, value)
589 return value
590 if hasattr(self, 'validate'):
--> 591 value = self.validate(obj, value)
592 if obj._cross_validation_lock is False:
593 value = self._cross_validate(obj, value)

C:\Users\Reddeda0\AppData\Local\Continuum\Miniconda3\lib\site-packages\ipywidgets\widgets\trait_types.py in validate(self, obj, value)
182 'be one of {}, but a value of '{}' was '
183 'specified.'.format(
--> 184 list(_number_format_types), format_type)
185 )

TraitError: The type specifier of a NumberFormat trait must be one of ['', 'o', 'b', '%', 'x', 'd', 'e', 'f', 'r', 'p', 'g', 's', 'c', 'X'], but a value of 'i' was specified.

[pbugnion]

Thanks for submitting an issue.

You are using a readout_format value of 'i' (presumably for a slider, but I can't tell exactly), which isn't actually a valid format. Previously, this was silently converted to a readout_format of ''. Part of the confusion is that the docs used 'i' in some places (despite it not being valid). I would just change that slider to use a readout format of '' (an empty string).

x.ref PR #1550 and issue #1544 .

[DougRzz]

Thanks v much. That fixed it.