How does a set in python store the elements?

[idknuttin]

I am coming learning python after working with c++ for a few years. In c++ when you insert into a set it orders the elements, I can't figure out why in python sometimes the set will order the elements and sometimes it does not. Here are a few examples:

a = set([3, 2, 1])
print(a)

prints: {1, 2, 3}

a = set([1, 2, 3])
print(a)

prints: {1, 2, 3}

a = set([5, 7, 9])
print(a)

prints: {9, 5, 7}

a = set([7, 9, 5])
print(a)

prints: {9, 5, 7}

a = set([5, 3, 7])
print(a)

prints: {3, 5, 7}

I don't know what's going on here, I know you can sort the set using sorted() but the way it originally stores the information doesn't make any sense to me.