from flask import Flask
from flask import render_template
app = Flask(__name__, template_folder='templates')
@app.route("/viewdata/")
def index1():
    return render_template('View-Data.html', id=1)
@app.route("/viewdata/<int:id>")
def index(id):
    return render_template('View-Data.html', id=id)
@app.errorhandler(404)
def page_not_found(e):
    return render_template('404.html'), 404
                                    
                                    
                                    
<!DOCTYPE html>
<html>
<head>
<title>Data</title>
</head>
<body>
<h1>You have entered {{ id }}</h1>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<title>Data</title>
</head>
<body>
<h1>Error in the Data</h1>
</body>
</html>