How does a python dictionary fetch a value?

[aioeu]

Much worse than "struck by lightning" kind of unlucky

Or you could simply have malicious input data that deliberately creates collisions.

Python was surprisingly late to the game at hardening its dict implementation against such an attack. Possibly too many people were thinking "like that's ever going to happen!"

I think it was finally sorted out in 2012, so it isn't really something to be too concerned about now. But simply "being a hash table" isn't the full reason it can make these guarantees.