Don't worry about it; males and females are basically identical externally (except that females usually get to be a bit larger as adults), and husbandry is the same for both sexes. I've had my ball python for almost 6 years, and only a few months ago I discovered that "she" might be a male. I'm still not sure either way, and I probably never will be. Many keepers acquire snakes from people who do not know the gender and keep the snake for its entire life without knowing. It seems weird, but hey, they don't care if we call them by the wrong pronoun.

If you really want to know, you can take the snake to a vet and have it probed. It is not a pleasant experience for the snake, and just not worth the money imo. Unless I suppose you're trying to breed the snake. Then you might want to know.