read_csv.py

import base64
import datetime
import io

import dash
from dash.dependencies import Input, Output, State
import dash_core_components as dcc
import dash_html_components as html
import dash_table

import pandas as pd


external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']


def csvDiv():
    csvDiv = html.Div([
        dcc.Upload(
            id='upload-data',
            children=html.Div([
                'Drag and Drop or ',
                html.A('Select Files')
            ]),
            
            # Allow multiple files to be uploaded
            multiple=True
        ),
        html.Div(id='output-data-upload'),
    ])
    return csvDiv


def parse_contents(contents, filename, date):
    content_type, content_string = contents.split(',')

    decoded = base64.b64decode(content_string)
    try:
        if 'csv' in filename:
            # Assume that the user uploaded a CSV file
            df = pd.read_csv(
                io.StringIO(decoded.decode('utf-8')))
            df.to_csv('.\\data\\saved_data.csv',sep=',',na_rep='NaN')
        elif 'xls' in filename:
            # Assume that the user uploaded an excel file
            df = pd.read_excel(io.BytesIO(decoded))
    except Exception as e:
        print(e)
        return html.Div([
            'There was an error processing this file.'
        ])
    return ( html.Div([ html.H5(filename),]) , [{'label' : f'{col}', 'value' : f'{col}'} for col in df.columns])