method to print name of an instance of a class

Question

I am new to classes and writing one to perform a tracking and timing task. Have looked at this but still having trouble getting one aspect of the functionality to work.

Here’s the part of what I’ve got to demonstrate the problem:

class seperate_trackers():

    def __init__(self): 
        print ("class initiated")

    def print_instance_name(self):
        print (self.__class__.__name__)

Create an instance of it:

track_task1 = separate_trackers()
>> class initiated

Run the method in there:

track_task1.print_instance_name()
>> separate_trackers

That’s not what I want!

How can that method be fixed so it returns track_task1 when it is run?

Asked By: cardamom

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Source

Answer 1

This is not a good idea. If you want your instance to have a name, that should be an attribute of the instance itself (the name of the variabe is just a pointer and it should not represent the object’s state).

Try this instead:

# We don't usually use snake case for class names in python (and its 'separate')
class SeparateTrackers():

    def __init__(self, name): 
        self.name = name


instance1 = SeparateTrackers("instance_name")

print(instance1.name) # instance_name

Answered By: Prateek Sanyal

Answer 2

Objects don’t know what variables refer to them. There can be any number of references to an object, and none of them is “the real one,” they are all equally valid as names for the object. Furthermore, there may be no references that are simple names:

things = [1, "hello", separate_trackers(), 3.14]

There’s no useful way to find out what variables refer to an object.

Answered By: Ned Batchelder

Answer 3

class SeparateTrackers:
  def __init__(self, instance_name):
    self.instance_name = instance_name

  def __str__(self):
    return self.instance_name

So you can use something like

a = SeparateTracker("first instance")
print(a) # print instance's name

Answered By: Emmanuel Mtali

Answer 4

Probably not something you’d want to rely on, but this is what I have if you’d like to mess around with it. Tested using python 3.11.0.

from inspect import currentframe, getframeinfo
from math import pi

class Circle:
    def __init__(self, radius):
        self.radius = radius
        
    def __call__(self):
        print(f'{self.get_caller_name()} called itself.')

    def area(self):
        print(f'{self.get_caller_name()} called area().')
        return pi * self.radius ** 2

    def get_caller_name(self):
        caller_frame = currentframe().f_back.f_back
        caller_locals = caller_frame.f_locals
        for name, obj in caller_locals.items():
            if obj is self:
                return name
        print("Could not determine the name referencing this instance.")
}

c1 = Circle(2)
c1()
c1.area()

Outputs:

> c1 called itself.
> c1 called area().

Answered By: ThinkingInBits

method to print name of an instance of a class

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