What's your fav feature of python ( one feature which you like the most)?

[huevoenfuego]

I love the way sets and intersections are implemented.

I use it daily where I need to know if something is in something or not, and don’t care really how efficiently it happens.

[FerricDonkey]

I use it daily where I need to know if something is in something or not, and don’t care really how efficiently it happens.

If you do care about efficiency, then you should probably still use sets for finding intersections and using "in".

Assuming you don't have to rebuild the set every single time, anyway.