CODEWITHSUNDEEP
pythonpython-2.7inheritancesuper
user1245262
user1245262

Reputation: 7505

How can I interpret this use of Python's super statement

I've been reading through some code and came across something that makes me think I understand super less well than I thought I did. What I saw was:

class Model(object):
    '''Abstract base model class.
    '''

    ...

    def get_config(self, verbose=0):
         '''Return the configuration of the model
            as a dictionary.

            To load a model from its configuration, use
            `keras.models.model_from_config(config, custom_objects={})`.
         '''
         config = super(Model, self).get_config()

Now, the Model class only inherits from object, so why is there a super? Does the object class have a get_config method ? (Not that I can see). Is this some sort of defensive programming technique, in case a class comes between object and Model? If so, how often & why does that sort of thing happen? If not, is there some other reason for this super?

Upvotes: 0

Views: 539

Answers (1)

Goodies
Goodies

Reputation: 4681

object does not have a valid instance method get_config() so this code, specifically, should not work. However, super essentially takes the parent class of a derived class. This is Python2 syntax. In Python3, you can simply call super() with no parameters.

Anyways, here's an example:

class Number(int):
    def __eq__(self, other):
        equal = super(Number, self).__eq__(other)
        print("{} and {} are {}equal".format(self, other, "not " if not equal else ""))
        return equal

    def __str__(self):
        return "Number({})".format(super(Number, self).__str__())

i = Number(5)
j = Number(7)
print(i == j) # Output:
"""
Number(5) and Number(7) are not equal
False
"""

This inherits from int and will modify the instance methods of int, while still being able to use the original methods.

In order for this code to work, you could overload the object class (I do not recommend this...).

class object(object):
    def __init__(self):
        pass

    def get_config(self):
        print("Getting object Config")
        return "config"


class Foo(object):
    def __init__(self):
        self.config = None

    def get_config(self):
        self.config = super(Foo, self).get_config()
        print("Getting Foo Config")

i = Foo()
i.get_config()
print(i.config)

Upvotes: 1

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