Pass variable to class for use by __init__

Question

I've a class

class Container(ContainerApp):
    def __init__(self, config,
                 image=None,
                 dns='a.b.c',
                 image_path=None,
                 ip=None):
    ...

It is used in the config of another class as follows:

class BasicTest(TestInterface):

    config = {
                'timeout': 1000,
                'api': MyAPI,
                'notification': Container,
    }
    ...

I want to pass an ip to be used by the Container class. I tried 'notification': Container(device_ip='1.1.1.1') in my config but it give me this error:

line 1650, in BasicTest
    'notification': Container(ip='1.1.1.1'),
TypeError: __init__() takes at least 2 arguments (2 given)

How do I do this?

Answer 1

It might not be the best solution, but it's doable this way:

config = {
    'timeout': 1000,
    'api': MyAPI,
#    'notification': Container,
}
config['notification'] = Container(config, ip='1.1.1.1')

Assuming that "this" config (in BasicTest ) is meant to be "that" config (passed to Container() ) too, and the question is the "recursion".

Answer 2

Reading between the lines that you want config['notification'] to be a type instead of an instance, ie that you will later instantiate it yourself, but you want to provide a default value for the ip parameter already:

from functools import partial

...

config = {
    'notification': partial(Container, ip='1.1.1.1')
}

An alternative would be lambda *args, **kwargs: Container(*args, ip='1.1.1.1', **kwargs) , which is essentially what partial papers over very nicely.

In other words, you want config['notification'] to be a callable (eg a function), which, when called, returns an instance of Container with a predefined value for one of its arguments.