Upload and show with flask a dataframe | AttributeError: 'builtin_function_or_method' object has no attribute 'replace' - dataframe

Question

I am trying to upload and show a dataframe by flask and when I want to show it, it says
AttributeError: 'builtin_function_or_method' object has no attribute 'replace'.
I found this code on YT and I don't know if it is correct. Can somebody help me?
from flask import Flask, render_template, request
from werkzeug.utils import secure_filename
import pandas as pd
import csv
def reencode(file):
for line in file:
yield line.decode('windows-1250').encode('utf-8')
#app.route("/data")
def data():
df = pd.read_csv("Sistema_de_Stock.csv", encoding='latin-1')
df = df.drop(df.loc['stock al cargar':].columns, axis=1)
df.to_html('data.html')
with open("data.html", 'r', encoding='latin-1') as file:
file = file.read
**file = file.replace("<table","<table class='rwd-table'")**
with open("data.html","w") as file_write:
file_write.write(html + file)
data = os.startfile("data.html")
return data

Answer 1

file.read is a method, so you should call the method. Furthermore you might want to rename the variable to make it clear that this is not a file handler:
with open('data.html', 'r', encoding='latin-1') as file:
# call the method ↓
file_data = file.read().replace('<table', "<table class='rwd-table'")
with open('data.html', 'w') as file_write:
file_write.write(html + file_data)
data = os.startfile('data.html')