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# See my issue at https://community.plotly.com/t/using-dcc-interval-for-continuous-update/41071/12 |
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import dash |
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from dash.dependencies import Input, Output |
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import dash_core_components as dcc |
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import dash_html_components as html |
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import logging |
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# from time import sleep |
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from tempfile import gettempdir |
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from os import getpid, remove |
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from os.path import join as pjoin, isfile |
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from dash.exceptions import PreventUpdate |
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tmpfile= pjoin(gettempdir(), f'time-{getpid()}') |
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if isfile(tmpfile): |
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remove(tmpfile) |
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external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css'] |
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app = dash.Dash(__name__, external_stylesheets=external_stylesheets) |
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log= logging.getLogger('werkzeug') |
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log.setLevel(logging.ERROR) |
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app.layout = html.Div([ |
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dcc.Input(id='total', value=0, type='number'), |
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html.Div(id='page-content'), |
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# the layout should update every 500 mili seconds |
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dcc.Interval(id= 'interval', n_intervals=0, interval=1000) |
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]) |
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@app.callback(Output('page-content', 'children'), |
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[Input('total', 'value'), Input('interval', 'n_intervals')]) |
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def display_page(value, n_intervals): |
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if isfile(tmpfile): |
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# read value from file |
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with open(tmpfile) as f: |
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value = f.read() |
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else: |
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# value is obtained from Input |
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pass |
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if not value or int(value)<1: |
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if isfile(tmpfile): |
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remove(tmpfile) |
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raise PreventUpdate |
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value= int(value) |
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value-= 1 |
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# write value back |
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with open(tmpfile, 'w') as f: |
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f.write(str(value)) |
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# return value |
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return html.Div([ |
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html.Plaintext(f'Value: {value}') |
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]) |
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if __name__ == '__main__': |
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app.run_server(debug=False) |
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