Currently the stdlib json module requires a custom serializer to avoid throwing a TypeError on collections.deque instances:

Python 3.3.4 (default, Feb 12 2014, 09:35:54) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from collections import deque
>>> import json
>>> d = deque(range(0, 10))
>>> json.dumps(d)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/json/__init__.py", line 233, in dumps
    return _default_encoder.encode(obj)
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/json/encoder.py", line 191, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/json/encoder.py", line 249, in iterencode
    return _iterencode(o, 0)
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/json/encoder.py", line 173, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: deque([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) is not JSON serializable