How do you flush stdout?

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I have the following:

import sys 

import os 

class Portfolio: 

    @classmethod 

    def menu(cls): 

        print("Main Menu") 

       p = Portfolio() 

       p.clear_screen()  

       p.transaction() 

    def clear_screen(self): 

        os.system('cls' if os.name == 'nt' else 'clear') 

         print(flush=True) 

        sys.stdout.flush() 

    def transaction(self): 

         print("Transaction Menu") 

if __name__ == "__main__" : Portfolio.menu()

When I run this the screen clears AFTER not BEFORE transaction() is run. How can I correct that?