bokeh streaming blank figure

Question

I'm trying to plot a real time line graph with Bokeh. But my code just plots a blank figure.

import numpy as np
from bokeh.models import ColumnDataSource
from bokeh.plotting import figure, curdoc


source = ColumnDataSource({'x': [], 'y': []})

def update():
    new = {'x':[np.random.rand(1,3)],
           'y':[np.random.rand(1,3)]}
    source.stream(new)

p = figure(plot_width=800,
           plot_height=400,
           x_range=[0, 1],
           y_range=[0, 1],
           x_axis_label = 'x',
           y_axis_label = 'y',
)
p.line(source=source, x='x', y='y')

curdoc().add_root(p)
curdoc().add_periodic_callback(update, 100)

Answer 1

Here is an instance of np.random.rand(1,3):

array([[0.60098985, 0.33777435, 0.92713769]])

It is an array of one element which is itself an array of 3 elements, so each element of 'x' and 'y' in your source is an array of 3 elements. Which is why nothing shows up.

You can use numpy.ndarray.flatten

def update():
    new = {'x':np.random.rand(1,3).flatten(),
           'y':np.random.rand(1,3).flatten()}
    source.stream(new)

Or just np.random.rand(3)