For those looking to validate dictionaries / JSON responses in Python, the voluptuous library works quite well: http://github.com/alecthomas/voluptuous. It also works for lists and other data types.
I use a fork/successor library, good[0], for configuration validation. I've especially liked the data transformation it can do (I can easily allow a configuration entry to be a single value, or list of values, and transform that to always be a list)
[0] https://github.com/kolypto/py-good