CODEWITHSUNDEEP
pythonplugins
Winston
Winston

Reputation: 1428

How to create a python plugin?

The following is the example I would like to do

I have different vehicle for Two-Door car, Bus, Van but they are the inherited from 'Vehicle'. What I want to do is to create a base class ('Vehicle') so everyone need to follow. And then people can build their own plugins (e.g. Bus, Van).

Then other users would use the plugin like this

my_vehicle = Vehicle('bus')

Then the bus class will be used.

I got the idea but I have no idea how should it be implemented?

Thanks in advance

Upvotes: 0

Views: 317

Answers (2)

James Mills
James Mills

Reputation: 19030

Another option is to use an already existing plugin library such as stevedore

This gives you:

  • A concise way to create plugins
  • Several ways to dynamically load them

Upvotes: 0

univerio
univerio

Reputation: 20518

You can use a metaclass for this:

class VehicleType(type):
    registry = {}

    def __init__(self, name, bases, attrs):
        self.registry[name.lower()] = self

    def __call__(self, name):
        cls = self.registry[name]
        inst = cls.__new__(cls)
        inst.__init__()
        return inst


class Vehicle(object):
    __metaclass__ = VehicleType


class Car(Vehicle):
    pass


car = Vehicle("car")
print(type(car))  # <class '__main__.Car'>

This works by having the class inheritance process register the class in the metaclass, then overriding the behavior of calling Vehicle so that it dynamically dispatches to the appropriate class.

Upvotes: 1

Related Questions