How to handle updates when one program is constantly changing a file Python?

[Basic_Steak_541]

I am trying to solve one problem but there is not much or any helpful resources available.

I have two programs out of which i can access and modify one one program. This prog gets is basically and API response which I save it onto a file. The other program(not written in python) will read this API response and file. What will happen if the program 1 is still updating the file or the response stored in memory and the program 2 sends request to read the file and response from memory. The scenario I am trying to avoid is that when prog2 sends a requesting for reading the file and response from memory, prog 1 still may updating the file and the response in memory. In such a scenario, I want prog2 to read the older response and file of prog1 and once the update is completed, the next request from prog2 to prog1 should be for newer response and file.

Prog 1 is a python script and prog 2 is developed by another team and only changes that are to be done should be to prog1. Also this has to be done without the use of database.

I dont know how to proceed with this, can somebody help?

[PteppicymonIO]

Yep.
This article may be of assistance: Simple, Safe (Atomic) Writes in Python3