While running the following code from Plotly Dash documentation page, for Prevent Callbacks From Being Executed on Initial Load, I got the following error:
TypeError: callback() got an unexpected keyword argument 'prevent_initial_call'
Here is the code
import dash
from dash.dependencies import Input, Output
import dash_html_components as html
from datetime import datetime
import time
app = dash.Dash()
app.layout = html.Div(
[
html.Button("execute callbacks", id="button_2"),
html.Div(children="callback not executed", id="first_output_2"),
html.Div(children="callback not executed", id="second_output_2"),
html.Div(children="callback not executed", id="third_output_2"),
html.Div(children="callback not executed", id="fourth_output_2"),
]
)
@app.callback(
Output("first_output_2", "children"),
Output("second_output_2", "children"),
Input("button_2", "n_clicks"), prevent_initial_call=True)
def first_callback(n):
now = datetime.now()
current_time = now.strftime("%H:%M:%S")
return ["in the first callback it is " + current_time, "in the first callback it is " + current_time]
@app.callback(
Output("third_output_2", "children"), Input("second_output_2", "children"), prevent_initial_call=True)
def second_callback(n):
time.sleep(2)
now = datetime.now()
current_time = now.strftime("%H:%M:%S")
return "in the second callback it is " + current_time
@app.callback(
Output("fourth_output_2", "children"),
Input("first_output_2", "children"),
Input("third_output_2", "children"), prevent_initial_call=True)
def third_output(n, m):
time.sleep(2)
now = datetime.now()
current_time = now.strftime("%H:%M:%S")
return "in the third callback it is " + current_time
if __name__ == '__main__':
app.run_server(debug=True)
Python version: 3.6 Dash version: 1.10.0
Does anyone know how to fix it? Thanks
