Question

I am writing a simple class that will basically accept 3 parameters, execute a series of commands and return the result.

Now the problem is that i am not clear about how to write a proper class in Python (i use C++ mainly); so is kinda weird for me to figure out what and how to write the class.

I have 3 parameters: name, classID and objectType (all 3 strings type), i need to return a string with the results of the operation.

So far I wrote this:

class testClass(superclass):

def __init__(self, name="",classID="", objectType="" *kwargs):

    superclass.__init__(self, args, **kwargs)

    result = ""
    ...(do the operation with the parameters, if the result is positive return OK
        otherwise return KO)

Then i saved it as testClass.py and imported it in my main python program

The issue is that when i pass parameters i get an error saying that the global name “args” is not defined, on the superclass __init line

In C I would just write something like

class testClass 
{
    string name, classID, objectType;
}string

and the program would know that it must expect 3 parameters (and then deal in the constructor with the data verification and validation), but i cannot grasp how you tell Python the same thing.

If i can get to understand how to use Python in the way that it should be (and not translating code from a language to another), maybe i can avoid to get stuck like in this case 🙂

Any help is appreciate to shed some light on the subject.

Answer 1

I think what you are looking for is the function definition thats like this def __init__(self, name="", classId="", objectType="", *args, **kwargs):.

What this defines besides the 3 known arguments (name, classId, objectType) is args which is a list of addtional arguments passed to the function, and kwargs which is a dictionary containing named arguments passed to the function.

With the above definition for your __init__ you could call your class this way:

t = testClass("name", "class1", "Object", "value1", 11, scope="local", destroy=True)

Now that call would give us inside __init__

name = "name"
classId= "class1"
objectType = "Object"
args =  ["value1", 11]
kwargs = { 'scope': "local",
           'destroy': True }

Oh and lastly, *args, **kwargs is optional for any function definition. If like you mention you know you will only be passed 3 arguments, then you can remove the *args, **kwargs.