So you think you know Python

Well, don't do that.

It's just a circular data structure, many (or even most) languages give you enough rope to hang yourself with one of those. Nothing particularly surprising or Python-specific about it.

foo = [bar[foo]]

bar[0] = foo

false

if wrong please correct accordingly.

What you have is a circular structure. foo and bar are distinct objects, so foo == bar is false. However, they are similar objects: they have exactly the same structure. If we had a function for structural comparison which handles cycles, that function would have to conclude that foo and bar are structurally equal. This is because of symmetry in the cycle: bar[0] is foo and, symmetrically, foo[0] is bar. Both foo and bar are one-element lists whose elements are, respectively, bar and foo.

There's a repo dedicated for such snippets: https://github.com/satwikkansal/wtfpython

I'm dissappointed.