Some comments:

1. Am I the only one that really loves that `print` is a statement and not a function? Call me lazy, but I don't mind not having to type additional parentheses.

5. Dict comprehensions can be dangerous, as keys that appear twice will be silently overridden:

  elements = [('a', 1), ('b', 2), ('a', 3)]
  {key: value for key, value in elements} == {'a': 3, 'b': 2}
  # same happens with the dict() constructor
  dict(elements) == {'a': 3, 'b': 2}

7. I see

  D.get(key, None)

way too often.

8. Unpacking works in many situations, basically whenever a new variable is introduced.

  for i, el in enumerate(['a', 'b']):
    print i, el

  {key: value for (key, value) in [('a', 1), ('b', 2), ('a', 3)]}

  map(lambda (x, y): x + y, [(1, 2), (5, -1)])

Note: the last example (`lambda`) requires parentheses in `(x, y)`, as `lambda x, y:` would declare a two-argument function, whereas `lambda (x, y):` is a one-argument function, that expects the argument to be a 2-tuple.