Grabbing the name of an instance in a class in python

Question

I have a class that is set up like this`

class Vehicle:
    def __init__(self, seats, wheels, engine):
        self.seats = seats
        self.wheels = wheels
        self.engine = engine

And I am given an instance like this

porsche = Vehicle(2, 4, "gas")

what I can't figure out is how to use the instance "porsche" to write out to the screen the names of each self initialization in the "__init__" section.

The desired output is a sentence like this:

"I have a Vehicle. It has seats, wheels, and an engine."

Where seats wheels and engine are coming from the class.

I retrieved Vehicle and put it into the string using this:

porsche.__class__.__name__

But for the life of me can't figure out how to get each self. object

Class instances don't have intrinsic names. If you want such a thing, add it to your `__init__`. — kindall, Aug 08 '17 at 23:35
Your question body doesn't seem to have anything to do with the title. — user2357112, Aug 08 '17 at 23:36
sorry, im just not sure how to ask the question. i don;t get how you can grab the names (seats, wheels, engine) and use them in strings — Jack Ingram, Aug 08 '17 at 23:40

score 1 · Answer 1 · answered Aug 09 '17 at 00:14

Your question seems to be asking how you can know the attribute names on your object. For simple objects (without slots), then its enough to inspect __dict__. So start with something like this:

def show(x):
    return "I have a {}. It has {}".format(type(x).__name__, ", ".join(x.__dict__))

Then

>>> show(Vehicle(1, 1, 1))
'I have a Vehicle. It has seats, wheels, engine'

score 1 · Answer 2 · answered Aug 09 '17 at 00:15

You can use obj.__dict__ to access an instance's fields / members / data attributes.

Are you looking for something like this?

class Vehicle:
    def __init__(self, seats, wheels, engine):
        self.seats = seats
        self.wheels = wheels
        self.engine = engine

    def description(self):
        # 'Vehicle'
        name = self.__class__.__name__

        # ['seats', 'wheels', 'engine']
        field_names = self.__dict__.keys()

        return "I have a %s. It has these fields: %s" % (
            name, ', '.join(field_names))


porsche = Vehicle(2, 4, "gas")
print(porsche.description())

Output:

I have a Vehicle. It has these fields: engine, wheels, seats

Note that these field names will be in an arbitrary order (dicts are unordered in Python), not necessarily in the order you defined them in __init__().

Grabbing the name of an instance in a class in python

2 Answers2