Get a variable from the URL in a Flask route

like this the example

@app.route('/profile/<username>')
def lihat_profile(username):
    return "welcome to profile page %s" % username

This is answered in the quickstart of the docs.

You want a variable URL, which you create by adding <name> placeholders in the URL and accepting corresponding name arguments in the view function.

@app.route('/landingpage<id>')  # /landingpageA
def landing_page(id):
    ...

More typically the parts of a URL are separated with /.

@app.route('/landingpage/<id>')  # /landingpage/A
def landing_page(id):
    ...

Use url_for to generate the URLs to the pages.

url_for('landing_page', id='A')
# /landingpage/A

You could also pass the value as part of the query string, and get it from the request, although if it's always required it's better to use the variable like above.

from flask import request

@app.route('/landingpage')
def landing_page():
    id = request.args['id']
    ...

# /landingpage?id=A