class Employee:                      # General superclass
    def computeSalary(self): …       # Common or default behaviors
    def giveRaise(self): …
    def promote(self): …
    def retire(self): …


class Engineer(Employee):            # Specialized subclass
     def computeSalary(self): …      # Something custom here


sue = Employee()                     # Default behavior
bob = Employee()                     # Default behavior
pat = Engineer()                     # Custom salary calculator


company = [sue, bob, pat]            # A composite object
for emp in company:
    print(emp.computeSalary())       # Run this object's version: default or custom


def processor(reader, converter, writer):
    while True:
        data = reader.read()
        if not data: break
        data = converter(data)
        writer.write(data)


class Reader:
    def other(self): …               # Default behavior and tools

class FileReader(Reader):
    def read(self): …                # Read from a local file

class SocketReader(Reader):
    def read(self): …                # Read from a network socket

…and others…

processor(FileReader(…),   converter,  FileWriter(…))
processor(SocketReader(…), converter,  FileWriter(…))
processor(FtpReader(…),    converter,  JsonWriter(…))