Containing_state_ex7

def find_containing_state(states):
    """Returns a function that takes a tweet and returns the name of the state
    containing the given tweet's location.

    Use the geo_distance function (already provided) to calculate distance
    in miles between two latitude-longitude positions.

    Arguments:
    tweet -- a tweet abstract data type
    us_states -- a dictionary from state names to positions.

    >>> sf = Tweet("Welcome to San Francisco", None, 38, -122)
    >>> ny = Tweet("Welcome to New York", None, 41.1, -74)
    >>> find_state = find_containing_state(us_states)
    >>> find_state(sf)
    'CA'
    >>> find_state(ny)
    'NY'
    """
    def find_state(tweet):
        for state in states:
            polygon = states[state]
            collisions = 0
            for i in range(len(polygon)-1):
                point_a = min(polygon[i], polygon[i+1],
                              key=lambda position: position.latitude())
                point_b = max(polygon[i], polygon[i+1],
                              key=lambda position: position.latitude())

                if not point_a.latitude() <= tweet.lat < point_b:
                    continue

                slope = (point_a.longitude() - point_b.longitude()) /\
                        (point_a.latitude() - point_b.longitude())

                y = slope*(tweet.lat - point_a.latitude()) +\
                    point_a.longitude()

                is_collision = y > tweet.lon
                collisions += is_collision

            if collisions%2 == INSIDE_MODULU:
                return state
        return None

    return find_state