How to trigger class method for multiple common interface classes?

If I have multiple classes with a common interface such as:

class RobotA:
    def do_smth(self):
        return 1

class RobotB:
    def do_smth(self):
        return 2

class RobotC:
    def do_smth(self):
        return 3

I want to run the do_smth method for each one (or for a sub-set of them) and get a list of the results.

Currently I do this with a simple function which takes an initialized class:

def do_smth(robots):
    return [robot.do_smth() for robot in robots]

However this requires me to initialize each robot as a parameter in the function:

robots = [RobotA(), RobotB(), RobotC()]
do_smth(robots)
>> [1, 2, 3]

Q: Is this good design to do?

Also, problem is that if I have 20 such robots, the list becomes large.

Q: Is there a neat way (design pattern maybe) to make this code more easy to maintain / elegant?