Python: call to self function not working correctly

Question

This seems like a very simple issue, and though I have a workaround I would like to fix it nicely.

EDIT: I am using a Django system, so the groups variable is actually inherited/retrieved from a DB) I just tried to make a minimal example, but I realised that that was not conducive to solving my issue

I have a class:

class Invite(models.Model, IndexedModelMixin):

    def get_associated_groups(self):
        return self.groups

But when I call get_associated_groups elsewhere

def get_groups(resource_object):
    resource_group_objects = resource_object.get_associated_groups()

where Invite is the resource_object, this error is thrown:

get_associated_groups() missing 1 required positional argument: 'self'

My workaround currently is

resource_group_objects = resource_object.get_associated_groups(resource_object)

Why isn't the self call implicit?

def __init__(self): self.groups = ... w3schools.com/python/python_classes.asp — Max
– Max, Commented Apr 24, 2019 at 8:15
@DeepSpace I edited the question, though maybe it's still the same issue? I can't really use __init__ with Django — Jessica Chambers
– Jessica Chambers, Commented Apr 24, 2019 at 8:20
It is most likely that resource_object is not an instance of Invite but a reference to the Invite class itself. Please do print(type(resource_object)) and verify the way you instantiate resource_object — DeepSpace
– DeepSpace, Commented Apr 24, 2019 at 8:31

JPG · Accepted Answer · 2019-04-24 08:43:42Z

where Invite is the resource_object, this error is thrown:

Here Invite is the class, it should be the class instance.

That is, You should pass the "instance of the Ivaite model/class" instead of the Invite class

invite_instance = Invite.objects.get(id=1)
get_groups(invite_instance) # calling the function

Reference
1. Python calling method in class

Example

In [3]: class Foo: 
   ...:     names = ["Tony", "George"] 
   ...:  
   ...:     def get_names(self): 
   ...:         return self.names 
   ...:  
   ...:  
   ...: def retrieve_names(foo_instance): 
   ...:     return foo_instance.get_names()                                                                                                                                                                        

In [4]:                                                                                                                                                                                                            

In [4]: retrieve_names(Foo)                                                                                                                                                                                        
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-3eb7dbe1c600> in <module>
----> 1 retrieve_names(Foo)

<ipython-input-3-dbb19979fd85> in retrieve_names(foo_instance)
      7 
      8 def retrieve_names(foo_instance):
----> 9     return foo_instance.get_names()

TypeError: get_names() missing 1 required positional argument: 'self'

In [5]:                                                                                                                                                                                                            

In [5]: foo_inst = Foo()                                                                                                                                                                                           

In [6]: retrieve_names(foo_inst)                                                                                                                                                                                   
Out[6]: ['Tony', 'George']

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