Defer data load¶
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import panel as pn
import pandas as pd
import hvplot.pandas
Defer loading of the data and populating the widgets until the page is rendered:
stocks_url = 'https://raw.githubusercontent.com/vega/datalib/master/test/data/stocks.csv'
select_ticker = pn.widgets.Select(name='Stock Ticker')
def load_data():
if 'stocks' not in pn.state.cache:
pn.state.cache['stocks'] = df = pd.read_csv(stocks_url, parse_dates=['date']).set_index('symbol')
else:
df = pn.state.cache['stocks']
symbols = list(df.index.unique())
select_ticker.options = symbols
select_ticker.value = symbols[0]
pn.state.onload(load_data)
If 'stocks' is not yet in cache we show a spinner widget, otherwise let us plot the data:
@pn.depends(select_ticker)
def plot_ticker(ticker):
if 'stocks' not in pn.state.cache or not ticker:
return pn.indicators.LoadingSpinner(value=True)
return pn.state.cache['stocks'].loc[ticker].hvplot.line('date', 'price')
pn.Row(select_ticker, plot_ticker).servable()
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Download this notebook from GitHub (right-click to download).