Why can't I update a whole range in a jupyter update

I was just helping a user on SO: http://stackoverflow.com/questions/35229507/set-x-axis-limit-in-bokeh-live-plot-embedded-in-jupyter-notebook/35343480#35343480

They were trying to do the following in an update function in a jupyter notebook:

fig.x_range = Range1d(min, max)
push_notebook()


This didn't work and in the end what was needed was:

fig.x_range.start = min
fig.x_range.end = max

push_notebook()

``


I thought the first thing was reasonable so thought I'd ask here in the hope of understanding something fundamental about how bokeh works.

Sincerely,

Sarah Bird