Edit:
Dictionary comprehensions only work in Python 2.7+. Since you are on Python 2.6, you can use dict
with a generator expression:
>>> X = [{'a': (123, 12445), 'b': (234, 34)}, {'a': (45666, 4), 'b': (3, 12)}]
>>> [dict((k, v[0]) for k,v in x.iteritems()) for x in X]
[{'b': 234, 'a': 123}, {'b': 3, 'a': 45666}]
>>>