How to run python function by clicking html button? - python-3.x

Question

I am trying to make this web app to work but I am getting an error. these are the steps that web app is supposed to handle:
import a file
run the python script
export the results
when I run python script independently( without interfering with flask), it works fine( I use Jupyter notebook) on the other hand, when I run it with flask (from prompt) I get an error:
File "app.py", line 88, in <module>
for name, df in transformed_dict.items():
NameError: name 'transformed_dict' is not defined
Any idea of how can I make this web app to work?
This is my first time using flask and I will appreciate any suggestions or guidance.
python file & html file
from flask import Flask,render_template,request,send_file
from flask_sqlalchemy import SQLAlchemy
import os
import pandas as pd
from openpyxl import load_workbook
import sqlalchemy as db
def transform(df):
# Some data processing here
return df
app=Flask(__name__)
#app.route('/')
def index():
return render_template('firstpage.html')
#app.route('/upload',methods=['Get','POST'])
def upload():
file=request.files['inputfile']
xls=pd.ExcelFile(file)
name_dict = {}
snames = xls.sheet_names
for sn in snames:
name_dict[sn] = xls.parse(sn)
for key, value in name_dict.items():
transform(value)
transformed_dict={}
for key, value in name_dict.items():
transformed_dict[key]=transform(value)
#### wirte to excel example:
writer = pd.ExcelWriter("MyData.xlsx", engine='xlsxwriter')
for name, df in transformed_dict.items():
df.to_excel(writer, sheet_name=name)
writer.save()
if __name__=='__main__':
app.run(port=5000)

Answer 1

Your block:
#### wirte to excel example:
writer = pd.ExcelWriter("MyData.xlsx", engine='xlsxwriter')
for name, df in transformed_dict.items():
df.to_excel(writer, sheet_name=name)
writer.save()
should be part of your upload() function since that's where you define and fill transformed_dict. You just need to match the indentation there to the block above it.
The current error is coming up because it's trying to run that code as soon as you start your script, and transformed_dict doesn't exist at that point.