This may seem simple and trivial, but today I discovered the basestring type in Python. It is essentially a base type for str and unicode, which comes in handy when writing isinstance(foo, basestring) in test code for example.
Strangely, despide PEP 237 mentioning the equivalent for int and long as "integer" I can't actually find what has become of that, so still writing isinstance(foo, (int, long)) for now.
Note that this is Python 2.x only, in 3.x it's all unicode so there is no longer a need for a common base type. int and long are unified as well in Python 3.x obviously.