calling a method from constructor in python

Question

I am trying call a child class method using parent class constructor.

class Configurator():
    config_file = "" #variable which stores config file
    input_response = "" #variable which stores input response json

    def __init__(self,config_file, input_response):
        self.config_file = config_file
        self.input_response = input_response

        config = ConfigParser.ConfigParser()
        config.read('config.cfg')
        if config.get('Configurator', 'ctool')  ==  'Chef':
            Configurator.__initialize(self)

    def __initialize(self):
        open_input_response = open(self.input_response, 'r')
        read_cloudprovider = json.load(open_input_response)
        cloudprovider = read_cloudprovider['CloudProvider']
        if cloudprovider == 'AWS':
            print('Working Here')
            obj = AWS()
            obj.print_test(self)


class AWS(Configurator):
    def print_test(self):
        print('I am AWS Class')


def main():
    configurator = Configurator('config.cfg', 'input_response.json')


if __name__ == '__main__':
    main()

Error:

TypeError: __init__() takes exactly 3 arguments (1 given)

Why im getting an error, AWS has no orguments to take

Side note: I strongly encourage you to check PEP 8 (and PEP 257): this will make your code more legible for you and others. This will in particular make it easier to answer your questions on StackOverflow. — Eric O. Lebigot
– Eric O. Lebigot, Commented Aug 7, 2014 at 13:19
The answers below are quite good. But it is quite odd that you are having your base class instantiate an instance of something that is a child class of itself. It implies that there is something odd going on in your code. — Bill Lynch
– Bill Lynch, Commented Aug 7, 2014 at 13:19

Ignacio Vazquez-Abrams · Accepted Answer · 2014-08-07 13:12:01Z

2

Methods that are not overridden in the child are the same method as in the parent. AWS.__init__() takes two additional arguments.

answered Aug 7, 2014 at 13:12

Ignacio Vazquez-Abrams

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Comments

Nikola Dimitroff · Accepted Answer · 2014-08-07 13:16:57Z

1

Take a look at the following segment:

 obj=AWS()
 obj.print_test(self)

You are constructing a new instance of the class AWS. What should python do when creating that instance? It must call AWS.__init__ but that method is nonexistent so it uses its parent - Configuration.__init__. The latter takes 3 arguments and this is why you see that error.

To fix that, you need to explicitly call Configuration.__init__ with the correct arguments:

class AWS:
    ...
    def __init__(self):
        Configuration.__init__(self, "value_for_config", "value_for_input")
        ...

Also, please note that in your current code Configuration.__init__ calls AWS.__init__ which calls Configuration.__init__ once again, this indirect recursion can easily lead to stack overflow so be careful.

answered Aug 7, 2014 at 13:16

Nikola Dimitroff

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1 Comment

user60679 Over a year ago

Error occurred while calling Configurator._init__ from AWS.__init__ Error: IOError: [Errno 2] No such file or directory: ''

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