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Live-updating plots with zmq, bqplot, and widgets¶

Start a simple zmq data publishing service, as a demo:

In [1]:

%%writefile publisher.py

import time
import pickle

import numpy as np
import zmq

size = 100
scale = 100
url = 'tcp://127.0.0.1:5555'

def main():
    ctx = zmq.Context.instance()
    pub = ctx.socket(zmq.PUB)
    pub.bind(url)
    while True:
        data = np.cumsum(np.random.randn(size)  * scale)
        md = {
            'shape': data.shape,
            'dtype': data.dtype,
        }
        pub.send_multipart([
                pickle.dumps(md, pickle.HIGHEST_PROTOCOL),
                data,
        ])
        time.sleep(1)

if __name__ == '__main__':
    main()

Overwriting publisher.py

In [2]:

from subprocess import Popen
publisher = Popen([sys.executable, 'publisher.py'])

Make an ipywidgets-based plot with bqplot:

In [5]:

import numpy as np
import bqplot as bq

size = 100
scale = 100.
np.random.seed(0)
x_data = np.arange(size)
y_data = np.cumsum(np.random.randn(size)  * scale)

x_sc = bq.LinearScale()
y_sc = bq.LinearScale()

ax_x = bq.Axis(label='X', scale=x_sc, grid_lines='solid')
ax_y = bq.Axis(label='Y', scale=y_sc, orientation='vertical', grid_lines='solid')

line = bq.Lines(x=x_data, y=y_data, scales={'x': x_sc, 'y': y_sc})
fig = bq.Figure(axes=[ax_x, ax_y], marks=[line], title='Live Updates!')
fig

Subscribe to our data-publisher, updating

In [4]:

import pickle

def subscribe(url):
    ctx = zmq.Context.instance()
    s = ctx.socket(zmq.SUB)
    s.connect('tcp://127.0.0.1:5555')
    s.subscribe = b''
    while True:
        pmd, buf = s.recv_multipart()
        md = pickle.loads(pmd)
        a = np.frombuffer(buf, dtype=md['dtype']).reshape(md['shape'])
        # setting line.y updates the plot above
        line.y = a


from threading import Thread

subscriber = Thread(target=subscribe, args=('tcp://127.0.0.1:5555',))
subscriber.start()