multiple-inheritance.py

#!/usr/bin/env python

class WorkerBase(object):
    def __init__(self, *args, **kwargs):
        print "WorkerBase init"
        pass

class DBWorker(WorkerBase):
    def __init__(self, *args, **kwargs):
        print "DBWorker init"
        print "DBworker config:", kwargs["config"]
        super(DBWorker, self).__init__(*args, **kwargs)

class LoggingWorker(WorkerBase):
    def __init__(self, *args, **kwargs):
        print "LoggingWorker init"
        print "LoggingWorker config:", kwargs["config"]
        super(LoggingWorker, self).__init__(*args, **kwargs)

class MyWorker(DBWorker, LoggingWorker):
    def __init__(self, *args, **kwargs):
        print "My worker init"
        super(MyWorker, self).__init__(*args, **kwargs)

if __name__ == "__main__":
    w = MyWorker(config="develop", hello="world")

"""
Demonstration for multiple inheritance.

Key notes:

* Your base classes (DBWorker, LoggingWorker) themselves have to extend a base
  class (not `object`), because __init__ needs to accept parameters (otherwise
  you get "TypeError: object.__init__() takes no parameters"
* Your base classes need to call super() to allow the other base classes to
  continue propagating. For example if DBWorker fails to call super(), then
  LoggingWorker's init function DOES NOT RUN. DBworker ends up halting the
  propagation of init functions.

The execution order of __init__ functions:

1. MyWorker
2. DBWorker
3. LoggingWorker
4. BaseWorker

If any of the __init__ functions fails to call super(), execution halts and
doesn't continue to the next one in the list.

Script output:

My worker init
DBWorker init
DBworker config: develop
LoggingWorker init
LoggingWorker config: develop
WorkerBase init
"""