Counter missing key behavior

Question

Accepted Answer

Counter is designed for counting, so accessing a missing key returns 0 instead of raising a KeyError. The letter 'h' appears once in 'hello', so `c['h']` is 1. 'z' is not in the string, but Counter silently returns 0 rather than throwing an error - unlike a regular dict, which would raise KeyError. This behavior makes frequency counting code much cleaner.