Update value of SLider

Community Support
1

I want to update automatically slider . But when i look at the terminal , my for loops finished but my slider didn’t change value or it changed too slowly.

s      = Slider(title="Value:", value = 0, step=1, end=1000,start=0)
update = Button(label='Update', width=20)
def update_value():
      n=0
      while n<1000:
         s.value+=1
         n+=1
      print(n)
update.on_click(update_value)
2

Is there a callback on the slider? What does it do?

3

There isn’t a callback. i just do like this. My idea is when you click a button your slider will move from 0 to 1000 step by step. This idea isn’t similar like you have a button “Play” using curdoc().add_periodic_callback. Do you have any advice for me?

4

Not offhand. If you can post a complete minimal example that I can copy/paste in to an editor and run locally, I am happy to do so and see if anything obvious turns up.

5 
from bokeh.models import Slider
from bokeh.models.widgets import Button
from bokeh.layouts import column
from bokeh.io import curdoc
import numpy as np
import pandas as pd

s      = Slider(title="Value:", value = 0, step=1, end=1000,start=0)
update = Button(label='Update', width=20)
def update_value():
    n=0
    while n<10000:
        list_slider111 = [0,1,0,0,0,0,0,0,0,0,0]
        ar14 = np.array(list_slider111)
        df14 = pd.DataFrame(ar14)
        out_name="Nb_images.txt"
        np.savetxt(out_name, df14, fmt='%1.2f', delimiter=",")
        print(n)
        s.value+=1
        n+=1
    print(n)
update.on_click(update_value)

curdoc().add_root(column(s,update))

This is one idea of my application. With my application there are a lot of things complicate in the for loops.
You can see, when the for loops finished, and the slider begins moving. How we can do it in parallel?

image
image1298×676 16.8 KB

6

The Python<->JavaScripy synchronization only happens at the end of a callback. If you update the same property many times in one callback, only the last value will have any effect. Every update needs to go in its own callback. The simplest way to do this is probably by setting up a periodic callback, e.g. how the Gapminder example does. You could also do something with add_next_tick_callback but it would probably have to be from a thread.

7

I used add_next_tick_callback. I have the same problem

8

As I mentioned, it would probably need to be from a thread. In any case, I can imagine many things this:

I used add_next_tick_callback. I have the same problem

might mean. Some of the possibly right, some of them not. So I can’t comment unless you share actual code for what you tried.