練習

rect.py

# coding: utf8
from __future__ import division, print_function, unicode_literals
from collections import namedtuple


class Point(namedtuple('Point', ('x', 'y'))):
    __slots__ = ()


class Rect(namedtuple('Rect', ('x', 'y', 'w', 'h'))):
    __slots__ = ()

    @classmethod
    def from_points(cls, (x1, y1), (x2, y2)):
        x = min(x1, x2)
        y = min(y1, y2)
        w = abs(x1 - x2)
        h = abs(y1 - y2)
        return Rect(x, y, w, h)

    @property
    def area((x, y, w, h)):
        return w * h

    def has((x, y, w, h), (px, py)):
        if (
            x <= px <= x + w and
            y <= py <= y + h
        ):
            return True
        return False

    def vertexes((x, y, w, h)):
        return (
            Point(x, y),
            Point(x + w, y),
            Point(x, y + h),
            Point(x + w, y + h),
        )

    def overlap(r1, r2):
        points_r1 = tuple(p for p in r1.vertexes() if r2.has(p))
        points_r2 = tuple(p for p in r2.vertexes() if r1.has(p))
        points = points_r1 + points_r2
        if points:
            return Rect.from_points(points[0], points[-1])
        return None


def similarity(rect1, rect2):
    rect3 = rect1.overlap(rect2)
    if rect3 is None:
        return 0
    return rect3.area / (rect1.area * rect2.area) ** .5

overlap の部分は、数学的にはただしい。
しかし、補足がないと、後で「なんだこりゃ」ってなりそう…。