Create an object without calling a class

Question

In matlab, I can create a structure array (struct) by doing the following.

person.name = 'Mike';
person.age = 25;
person.gender = 'male';

wherein person is not defined prior to creating the struct. When I try to do it in python, it gives me an error

name 'person' is not defined

Is there a similar way of doing it in python? Thanks

EDIT: Being new to python, I still think in matlab. The problem that I have is that I have a function that will take multiple inputs (more than 40), so instead of having function(input1,input2,...,input40), I will just have function(input) where the input consist of input.1, input.2,.., input.40.

Answer 1

In Python you can add members dynamically to an object, but (1) the name must already exist (it must have been assigned) and (2) it must be bound to an instance of some class. To do so you may create an empty class:

class Empty:
    pass        # empty statement otherwise the class declaration cannot succeed

construct an instance of it and assign it to your variable

person = Empty()

and then add whatever data you want

person.name = 'Mike'
person.age = 25
person.gender = 'male'

On the other hand, if you don't need the additional features a "normal" class provides and you just want to store some data in a key=>value fashion you should probably just use a dictionary.

person={}
person['name']='Mike'
person['age']=25
person['gender']='male'

(notice that, at least up to Python 2.7, this is mostly just a stylistic/syntactic difference, since instance members are implemented underneath in terms of dictionaries)

As a general guideline, you want classes when you are instantiating multiple objects made in the same way (and where typically the assignment to the members is done in the class constructor; adding members later generally makes for difficult to follow code), dictionaries otherwise.