Retrieve from email and save to the database Python Flask PostgreSQL

Question

I am trying to improve a user registration mechanism (I am using Flask and PostgreSQL) and I have an issue, so my question is:

• The admin make an invitation email for a new user (the admin enter an email for a new user and save it to the database)
• User opens that email and clicks on the invitation link, enter a new password (this saved his password to the database)

My question is how I can retrieve information from which email the user loaded the link, because at the moment the user can enter what email he wants, but I need in some way the email will be already there (the email is already at the database when admin saved it at the first step) and user will enter only the password (and save it to the database).