from flask import Flask, g, request, session, redirect, url_for
from flask.ext.simpleldap import LDAP

app = Flask(__name__)
app.secret_key = 'dev key'
app.debug = True

app.config['LDAP_HOST'] = 'ldap.example.org'
app.config['LDAP_BASE_DN'] = 'OU=users,dc=example,dc=org'
app.config['LDAP_USERNAME'] = 'CN=user,OU=Users,DC=example,DC=org'
app.config['LDAP_PASSWORD'] = 'password'

ldap = LDAP(app)

@app.route('/')
@ldap.basic_auth_required
def index():
    return "Welcome, {0}!".format(g.ldap_username)

if __name__ == '__main__':
    app.run()

Add an example of using .basic_auth_required()