Python - Input in composite field

[Kasper Aamodt]

Is there a way to copy a text string from one variable to another, without it pointing at it, so it just looks like a string to the compiler(if that is the right word)? Im trying to make an account budget with the google ads api, and to set a start date, you have to hard code in a string with the date, but i want to be able to change the start date for each budget. It wont work with input, or reading a string from a file, i get this error:

AttributeError: Assignment not allowed to composite field "proposed_start_date_time" in protocol message object.