Use a LibreOffice or Word document as a template and fill in the values from python. Mail merge from python.
This is a very dirty program. You probably don't want to use it. You probably want to learn how to use mail merge.
Write a LibreOffice Writer or MS Word document and use standard python placeholders in the format {firstname}. Then you can use this moudle to replace the placeholders with values from a dictionary.
In Word, all placeholders have to be spelled correctly or spell check must be turned off. Word saves the red underlined words in a way that disables the mail merge.