How to make a variable available accross all open flask sessions
You should use a database to achieve that, if your project is not big, SQLite should be enough, and Flask-SQLAlchemy would be a good choice to make the persistent work easier.
I am writing a rest api in flask to read data from some json files, turn them to pandas dataframes, read and/or edit data from the data frames. When I turn the jsons into dataframes I want to make sure that any finite number of computers that access the api now has access to the same dataframes, and assuming computer A edits a data frame(maybe deletes a column called "names") , then when computers B-Z try to access the names column in tbe data frame it should also be gone for them. How do I achieve this in a flask emvironment. i already tried reading the files and declaring the dataframes at the start of the flask app but when i looked online for a bit i found that it's bad practice to  use global varibles in flask. All the help i found siggested using sessions, but that would mean the changes computer A makes to the dataframe, will be visible to only computer A unless it saves back to the json file and all other computer B-Z re-read from the Json. Thanks for your help.