from enum import Enum 
from abc import ABCMeta, abstractmethod 
 
State = Enum('State', 'new running sleeping restart zombie') 
 
class User: 
    pass 
 
class Process: 
    pass 
 
class File: 
    pass 
 
class Server(metaclass=ABCMeta): 
    @abstractmethod 
    def __init__(self): 
        pass 
 
    def __str__(self): 
        return self.name 
 
    @abstractmethod 
    def boot(self): 
        pass 
 
    @abstractmethod  
    def kill(self, restart=True): 
        pass 
 
class FileServer(Server): 
    def __init__(self): 
        '''actions required for initializing the file server''' 
        self.name = 'FileServer' 
        self.state = State.new 
 
    def boot(self): 
        print(f'booting the {self}') 
        '''actions required for booting the file server''' 
        self.state = State.running 
 
    def kill(self, restart=True): 
        print(f'Killing {self}') 
        '''actions required for killing the file server''' 
        self.state = State.restart if restart else State.zombie 
 
    def create_file(self, user, name, permissions): 
        '''check validity of permissions, user rights, etc.''' 
        print(f"trying to create the file '{name}' for user '{user}' with permissions {permissions}") 
 
class ProcessServer(Server): 
    def __init__(self): 
        '''actions required for initializing the process server''' 
        self.name = 'ProcessServer' 
        self.state = State.new 
 
    def boot(self): 
        print(f'booting the {self}') 
        '''actions required for booting the process server''' 
        self.state = State.running 
 
    def kill(self, restart=True): 
        print(f'Killing {self}') 
        '''actions required for killing the process server''' 
        self.state = State.restart if restart else State.zombie 
 
    def create_process(self, user, name): 
        '''check user rights, generate PID, etc.''' 
        print(f"trying to create the process '{name}' for user '{user}'") 
 
class WindowServer: 
    pass 
 
class NetworkServer: 
    pass 
 
class OperatingSystem: 
    '''The Facade''' 
    def __init__(self): 
        self.fs = FileServer() 
        self.ps = ProcessServer() 
 
    def start(self): 
        [i.boot() for i in (self.fs, self.ps)] 
 
    def create_file(self, user, name, permissions): 
        return self.fs.create_file(user, name, permissions) 
 
    def create_process(self, user, name): 
        return self.ps.create_process(user, name) 
 
def main(): 
    os = OperatingSystem() 
    os.start()  
    os.create_file('foo', 'hello', '-rw-r-r') 
    os.create_process('bar', 'ls /tmp') 
 
if __name__ == '__main__': 
    main()