Reset WordPress user passwords and send them a new user notification email. Read the comments. BE CAREFUL WITH THIS CODE!

wordpress_mass_password_reset.php

/*
  Place this code inside your active theme's functions.php or in a custom plugin
*/
function my_password_reset()
{
  //get all users you just added
  $user_ids = $wpdb->get_col("SELECT ID FROM $wpdb->users WHERE ID > 1");	//change 1 here to the ID of the first imported user
   
  //$user_ids = array(6,7);    //if you want to test on a couple users first. enter ids for two test accounts you will get email from.
   
  //now loop through the users
  foreach($user_ids as $user_id)
  {
  	//create a new password
  	$newpass = pmpro_getDiscountCode();		//returns a psuedo random 10 character code
   
  	//update the user's password
  	$userdata = array("ID" => $user_id, "password" => $newpass);
  	wp_update_user($userdata);
   
  	//send the notification email
  	wp_new_user_notification($user_id, $newpass);		
   
  	echo ".";	//so we can see progress
  }
   
  echo "done";
  exit;
}
add_action("init", "my_password_reset");

This recipe is included in the blog post on "How to Mass Import Members into WordPress/PMPro" at Paid Memberships Pro here: https://www.paidmembershipspro.com/how-to-mass-import-members-into-wordpresspmpro/