sdk-for-flutter/docs/examples/account/update-password.md

import 'package:appwrite/appwrite.dart';

Client client = Client()
    .setEndpoint('https://<REGION>.cloud.appwrite.io/v1') // Your API Endpoint
    .setProject('<YOUR_PROJECT_ID>'); // Your project ID

Account account = Account(client);

User result = await account.updatePassword(
    password: '',
    oldPassword: 'password', // optional
);