Clear previous output of widget every time it runs

Question

I would like to clear the previous output when the widget is rerun.

for example

from IPython.display import display, clear_output

import ipywidgets as widgets
from datetime import datetime, timedelta

button = widgets.Button(description='RUN',button_style='info')

def on_button_clicked(b):

    # DO SOMETHING #

    out = widgets.Output()
    out.clear_output(wait=True)
    out.append_stdout(f'Ran at {datetime.now()}')
    display(out)

button.on_click(on_button_clicked)
widgets.VBox([button])

Every time i click on the RUN button it "appends" the print statement

I also tried this:

button = widgets.Button(description='RUN',button_style='info')

def on_button_clicked(b):

    # DO SOMETHING #

    out = widgets.Output()
    out.clear_output(wait=True)
    with out:
        print(f'Ran at {datetime.now()}')
    display(out)

button.on_click(on_button_clicked)
widgets.VBox([button])

NameError: name 'button' is not defined

Reblochon Masque
– Reblochon Masque

2020-05-29 08:12:09 +00:00
Commented May 29, 2020 at 8:12 — Reblochon Masque
– Reblochon Masque, Commented May 29, 2020 at 8:12

dimitris_ps · Accepted Answer · 2020-05-29 08:55:38Z

2

This works


from IPython.display import display, clear_output

import ipywidgets as widgets
from datetime import datetime, timedelta


button = widgets.Button(description='RUN',button_style='info')

out = widgets.Output() 

@out.capture(clear_output=True)
def on_button_clicked(b):
    # DO SOMETHING #
    print ( f'Ran at {datetime.now()}')


button.on_click(on_button_clicked)
widgets.VBox([button])

answered May 29, 2020 at 8:55

dimitris_ps

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Comments

DV82XL · Accepted Answer · 2020-05-31 17:06:52Z

Looks like you're running ipython 3.8... that's 5 years old. I strongly recommend upgrading to a later version, but totally understand that this is not always possible depending on time and resources.

Here's the documentation for the ipython 3.x display widget:
https://ipython.org/ipython-doc/3/api/generated/IPython.display.html#functions

Try this:

from IPython.display import clear_output
import ipywidgets as widgets
from datetime import datetime

button = widgets.Button(description='RUN',button_style='info')

def on_button_clicked(b):
    # DO SOMETHING #
    print(f'Ran at {datetime.now()}')

    # This will clear the cell output the NEXT time the button is pressed
    clear_output(wait=True)

button.on_click(on_button_clicked)
widgets.VBox([button])

There have been some reports of "shaking" in the notebook when print() is used. If you notice this, try using print('message', flush=True) instead.

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