I don't mean to be rude, but I would like to chip in and back up Taine here.
The 'or' operator: - Already unambiguously associated with a logical OR, which is effectively what takes place in this circumstance. Using a different symbol to have the same effect is bound to be confusing to a reasonably large number of people.
The '|' character: - Saves one character, but I think it would be easier to miss compared to a keyword which is easy to highlight in an editor. - It's existing usages are very context-specific (between two dict objects, within a regex expression) - using it here I think would start to bring it into the language in a more general way. Because of this, I think a more holistic discussion on its place within Python is appropriate before it is reached for as a bespoke solution.