proxy.py

import time 

class SalesManager:             
    def work(self):                         
        print("Sales Manager working...")             

    def talk(self):                         
        print("Sales Manager ready to talk") 

class Proxy:             
    def __init__(self):                         
        self.busy = 'No'                         
        self.sales = None             

    def work (self):                         
        print("Proxy checking for Sales Manager availability")                         
        if self.busy == 'No':                                      
            self.sales = SalesManager()                                      
            time.sleep(2);                                      
            self.sales.talk()                         
        else:                                      
            time.sleep(2);                                      
            print("Sales Manager is busy") 

if __name__ == '__main__':
    p = Proxy()
    p.work()
    p.busy = 'Yes'
    p.work()