Date Range picker

Dash Python
1

Hello all !

I am trying to build this web app for practice. I am using a date range picker where the app should be able to populate a graph of cumulative returns of SPY during the time period selected.

Problem,: I am unable to select dates, only few dates can be selected by default. Also I am getting this warning :

A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

I would appreciate any help, Thanks ! I have the code below –

import pandas as pd
import plotly.express as px
import seaborn as sns
import yfinance as yf

spy = yf.download("SPY",start = "2000-01-01", end = "2023-12-01" )
spy = spy.reset_index().head()

from dash import Dash, html, dcc
import dash_daq as daq
from dash.dependencies import Output, Input
from dash.exceptions import PreventUpdate
import dash_bootstrap_components as dbc
from dash_bootstrap_templates import load_figure_template
from datetime import datetime
from datetime import date

load_figure_template("SLATE")

app = Dash(__name__,external_stylesheets=[dbc.themes.SLATE])

app.layout = html.Div([
    
    dbc.Row([
        
        html.H2("SPY Returns", style = {"text-align":"center"}),
        
        dbc.Col([
            html.Div([
            html.H4("Pick a Date"), 
            dcc.DatePickerRange(
                id = "date_picker",
                min_date_allowed = spy["Date"].min(),
                max_date_allowed = spy["Date"].max(),
                initial_visible_month = spy["Date"].max(),
                start_date = spy["Date"].min(),
                end_date = spy["Date"].min())
            
        ]),
            dbc.Col([
                html.Div([
                    dcc.Graph(id = "graph")
                ])
                
            ])
    ])
    
    ])
    
])

@app.callback(
        Output("graph","figure"),
        [Input("date_picker", "start_date"), Input("date_picker", "end_date")]
        )

def plot_graph(start_date, end_date):
    df = spy.loc[spy["Date"].between(start_date, end_date)]
    df["returns"] = df["Adj Close"].pct_change(1).dropna()
    df["cum_returns"] = (1 + df["returns"].cumprod()-1)*100
    #pct_return = df["cum_returns"].iloc[-1]-df["cum_returns"].iloc[0] 
    
    fig = px.line(df,
                 x = df["Date"],
                 y = "cum_returns",
                 title = "Cumulate SPY Returns %")
    return fig

if __name__ == "__main__":
    app.run(debug= True, port = 2525, jupyter_mode = 'external')
2

Hello again @puns,

you need to get rid of head() from the code below.

spy = yf.download("SPY",start = "2000-01-01", end = "2023-12-01" )
spy = spy.reset_index().head()

Cheers!

3

Hey, thanks a lot Berbere!!