does the f-string convert an integer to a string?

Question

Hello I was practicing using loops and I saw that while using concatenation I have to convert int's to strings, but then I saw that if I use a f-string I dont need convert it to an int.

Here is the code:

# some code up there

average_cost = [total_cost / len(actual_insurance_costs)]

# using a f-string
print(f"Average Insurance Cost: {average_cost} dollars.")

# using concatenation
print("Average Insurance Cost: " + str(average_cost) + " dollars.")

So does the f-string convert an int into a string?

Answer 1

Yes, it does, by way of calling format(...) on it, which in turn calls __format__() on the object.

That extends to everything else too, including objects with a custom __format__(). For instance,

class Thing:
    def __format__(self, format_spec):
        return f"I don't like being formatted with {format_spec!r}!"


print(f"This is a thing: {Thing():>10}")

prints out

This is a thing: I don't like being formatted with '>10'!

(The default implementation of __format__() just calls __str__().)