Look at the code presented in the editor pane.
- There is a “Base_Computer” class that represents a generic computer. A generic computer has only a serial number;
- there is a “Personal_Computer” class that is built upon the “Base_Computer” class and represents a computer that is able to connect to the internet;
- there is a generic “Connection” class that holds information about the connection speed and handles the
download()method. This class is independent of any computer class; - there are the “Connection” subclasses, more specialized than the “Connection” class:
- “Dialup”
- “ADSL”
- “Ethernet”
* When we start with our personal computer, we set the serial number to 1995 and equip it with a dialup connection. This an example of composition.
- It is possible to download some data using a slow dialup connection;
- later, we equip our personal computer with a more advanced connection device. There is no need to recreate the computer object – we just arm it with a new component;
- the last steps are about arming our old computer with a fast connection and downloading some data.
When you run the code, you should see the following:
The computer costs $1000
Dialling the access number ... Downloading at 9600bit/s
Waking up modem ... Downloading at 2Mbit/s
Constantly connected... Downloading at 10Mbit/s
output
Code
class Base_Computer:def __init__(self, serial_number):
self.serial_number = serial_number
class Personal_Computer(Base_Computer):
def __init__(self, sn, connection):
super().__init__(sn)
self.connection = connection
print('The computer costs $1000')
class Connection:
def __init__(self, speed):
self.speed = speed
def download(self):
print('Downloading at {}'.format(self.speed))
class DialUp(Connection):
def __init__(self):
super().__init__('9600bit/s')
def download(self):
print('Dialling the access number ... '.ljust(40), end='')
super().download()
class ADSL(Connection):
def __init__(self):
super().__init__('2Mbit/s')
def download(self):
print('Waking up modem ... '.ljust(40), end='')
super().download()
class Ethernet(Connection):
def __init__(self):
super().__init__('10Mbit/s')
def download(self):
print('Constantly connected... '.ljust(40), end='')
super().download()
# I started my IT adventure with an old-school dial up connection
my_computer = Personal_Computer('1995', DialUp())
my_computer.connection.download()
# then in the year 1999 I got ADSL
my_computer.connection = ADSL()
my_computer.connection.download()
# finally I upgraded to Ethernet
my_computer.connection = Ethernet()
my_computer.connection.download()
{{ dockerServerErrorMsg }}
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