Python Coroutines and Counters

The collections module, since Python 2.4, includes a Counter type. I wondered, when I first saw this class, how useful could a counter possibly be? It turns out, very useful. You can do a lot with counters because of their flexibility in terms of what they can count. For instance, you can pass a counter a list of strings, a dictionary who's values represent counts, or strings, where each unique character is counted.