'order' of unordered Python sets

Question

I understand that sets in Python are unordered, but I\'m curious about the \'order\' they\'re displayed in, as it seems to be consistent. They seem to be out-of-order in the

Answer 1

The reason of such behavior is than Python use hash tables for dictionary implementation: https://en.wikipedia.org/wiki/Hash_table#Open_addressing

Position of the key is defined by it's memory address. If you know Python reuse memory for some objects:

>>> a = 'Hello world'
>>> id(a)
140058096568768
>>> a = 'Hello world'
>>> id(a)
140058096568480

You can see that object a has different address every time it's init.

But for small integers it isn't change:

>>> a = 1
>>> id(a)
40060856
>>> a = 1
>>> id(a)
40060856

Even if we create second object with different name it would be the same:

>>> b = 1
>>> id(b)
40060856

This approach allow to save memory which Python interpreter consume.