Graph and ipywidget cannot be in same code cell when using %matplotlib notebook

Question

I want to make a figure and interactively change it with ipywidgets. When I use %matplotlib notebook, the widget call needs to be in a separate code cell, which is odd. Here is the code that doesn't work

import matplotlib.pyplot as plt
from matplotlib.patches import Circle
%matplotlib notebook

fig = plt.figure(figsize=(6, 6))
ax1 = plt.subplot(111, aspect='equal')
ax1.set_xlim(-5,5)
ax1.set_ylim(-5,5)
circ = Circle((0,0), radius=1)
ax1.add_patch(circ)

def change_radius(r=1):
    circ.set_radius(r)

from ipywidgets import interact
interact(change_radius, r=(1.0, 5))

This only works when the last two lines are in a separate code cell, but then the widget is separated from the graph by the code cell. Does anybody know how to get it to work in one code cell with %matplotlib notebook ?

I think this is a limitation of the current implementation (which does not directly use ipywidgets but injects a good bit of custom js) which does not play as well with the display machinery as it should. — tacaswell
– tacaswell, Commented Mar 18, 2016 at 2:10
That's what I was worried about. Is this something that can be changed, or does that require a complete overhaul of the current implementation? — Mark Bakker
– Mark Bakker, Commented Mar 18, 2016 at 8:46

nluigi · Accepted Answer · 2016-03-18 16:22:14Z

2

You should call the figure explicitly using display(fig) in change_radius():

import matplotlib.pyplot as plt
from matplotlib.patches import Circle
from IPython.display import display
%matplotlib notebook

fig = plt.figure(figsize=(6, 6))
ax1 = plt.subplot(111, aspect='equal')
ax1.set_xlim(-5,5)
ax1.set_ylim(-5,5)
circ = Circle((0,0), radius=1)
ax1.add_patch(circ)

def change_radius(r=1):
    circ.set_radius(r)
    display(fig)

from ipywidgets import interact
interact(change_radius, r=(1.0, 5))

answered Mar 18, 2016 at 16:22

nluigi

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1 Comment

nluigi Over a year ago

@MarkBakker No problem! make sure you also check out the ipywidget examples at their github repo. They are a useful source of info.

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