More concise handling of request parameters.

gistfile1.pyw

def get_many(d, required=[], optional=[], one_of=[]):
    """
    Returns a predictable number of elements out of `d` in a list for auto-expanding.

    Keys in `required` will raise KeyError if not found in `d`.
    Keys in `optional` will return None if not found in `d`.
    Keys in `one_of` will raise KeyError if none exist, otherwise return the first in `d`.

    Example usage:

        uid, action, limit, offset = get_many(request.params, required=['uid', 'action'], optional=['limit', 'offset'])

    """
    d = d or {}
    r = [d[k] for k in required]
    r += [d.get(k)for k in optional]

    if one_of:
        for k in (k for k in one_of if k in d):
            return r + [d[k]]

        raise KeyError("Missing a one_of value.")

    return r

gistfile2.pyw

# Unit tests for get_many

    def test_get_many(self):
        params = dict((n,n) for n in range(5)) # Dict with keys and values of 0, 1, 2, 3, 4

        self.assertEqual(get_many(params), [])
        self.assertEqual(get_many(params, required=[1, 2]), [1, 2])
        self.assertEqual(get_many(params, optional=[1, 2]), [1, 2])
        self.assertEqual(get_many(params, optional=[6, 7, 8]), [None, None, None])
        self.assertEqual(get_many(params, one_of=[1, 2]), [1])
        self.assertEqual(get_many(params, one_of=[6, 1]), [1])

        self.assertEqual(get_many(params, optional=[6, 1]), [None, 1])
        self.assertEqual(get_many(params, required=[1, 2], optional=[6, 1]), [1, 2, None, 1])
        self.assertEqual(get_many(params, required=[1, 2], optional=[6, 1], one_of=[7, 8, 3]), [1, 2, None, 1, 3])

        self.assertRaises(KeyError, get_many, params, required=[1, 6])
        self.assertRaises(KeyError, get_many, params, one_of=[7, 6])