I’m trying to learn and understand dependency injection. (python example below):

class Printer :
    def print(self):
        pass


class CSVPrinter(Printer) :
    def print(self, data):
        for i in data:
            print(str(i)+ ";", end ="")


class PlainPrinter(Printer) :
    def print(self, data):
        for i in data:
            print(str(i)+ " ", end ="")

class Product:  
    def __init__(self, name, price, printer):
        self.name = name
        self.price = price
        self.printer = printer 
    def print(self):
        tab=[self.name, self.price]
        self.printer.print(tab)
 
printer = PlainPrinter()
prod = Product("prod1", "22", printer)
prod.print()

So I do understand, that doing it, I can simply inject PlainPrinter or CSVPrinter into Product, so that Product can behave in a different way.
But in both cases, I need to somehow pass Product’s data outside (to the Printer) so that it can operate on it (like in the Product.print())…
-so in fact I could also have some “getter” in Product, that returns data, and then I can operate on it, without any coupling at all, so what’s the point?