I wouldn't be totally surprised if the reason Python disallows custom operators is because it either requires a lot more context in the parser or a lot of care

I wouldn't be totally surprised if the reason Python disallows custom operators is because it either requires a lot more context in the parser or a lot of care in how they're used (or a hack re-using existing operators like TFA). Neither option is without its costs. Languages that have them usually opt for the former. E.g., in Python `foo|bar` is totally unambiguous right now, give or take some nuance as to whether it's in a string/comment/whatever, but outside that tiny bit of context it's clear what's a variable and what's an operator. As soon as I can define `oo` and `|ba` as operators though it's a lot less clear what's going on, and all parsers (including editors, not just the cpython interpreter) need to be able to understand those semantics to work reliably. Edit: I'm having a tiny bit of trouble finding it, but my memory just came back to me, and there's a PEP floating around where Guido's rationale was just that there wasn't a solid use case so it wasn't worth implementing. Later the numpy folks introduced the @ symbol as a solid use case (matrix multiply), but nobody could come up with a sufficiently convincing argument for arbitrary operators -- we gained the @ operator and don't have the rest.