这是一个如何从代码中使其成为 函子 对象并使用它的示例，以及对一些我认为值得的其他事情的更改。函子是充当功能的实体，但可以像对象一样对其进行操作。
在Python中，由于函数已经是单例对象，因此两者之间的区别较小，但是有时为一个对象创建专用类很有用。在这种情况下，它允许将辅助函数做成私有类方法，而不是您似乎反对这样做的全局或嵌套方法。
from math import atan2, cos, pi, sinclass GetMinimumAreaRectangle(object): """ functor to find length, width, and area of the smallest rectangular area of the given convex hull """ def __call__(self, hull): self.hull = hull mostfar = self._mostfar # local reference n = len(hull) min_area = 10**100 # huge value iL = iR = iP = 1 # indexes left, right, opposite# print ' {:>2s} {:>2s} {:>2s} {:>2s} {:>9s}'.format(# 'i', 'iL', 'iP', 'iR', 'area') for i in xrange(n-1): dx = hull[i+1][0] - hull[i][0] # distance on x axis dy = hull[i+1][1] - hull[i][1] # distance on y axis theta = pi-atan2(dy, dx) # get orientation angle of the edge s, c = sin(theta), cos(theta) yC = hull[i][0]*s + hull[i][1]*c xP, yP, iP = mostfar(iP, n, s, c, 0, 1) if i==0: iR = iP xR, yR, iR = mostfar(iR, n, s, c, 1, 0) xL, yL, iL = mostfar(iL, n, s, c, -1, 0) l, w = (yP-yC), (xR-xL) area = l*w# print ' {:2d} {:2d} {:2d} {:2d} {:9.3f}'.format(i, iL, iP, iR, area) if area < min_area: min_area, min_length, min_width = area, l, w return (min_length, min_width, min_area) def _mostfar(self, j, n, s, c, mx, my): """ advance j to extreme point """ hull = self.hull # local reference xn, yn = hull[j][0], hull[j][1] rx, ry = xn*c - yn*s, xn*s + yn*c best = mx*rx + my*ry while True: x, y = rx, ry xn, yn = hull[(j+1)%n][0], hull[(j+1)%n][1] rx, ry = xn*c - yn*s, xn*s + yn*c if mx*rx + my*ry >= best: j = (j+1)%n best = mx*rx + my*ry else: return (x, y, j)if __name__ == '__main__': hull= [(560023.44957588764, 6362057.3904932579),(560023.44957588764, 6362060.3904932579),(560024.44957588764, 6362063.3904932579),(560026.94957588764, 6362068.3904932579),(560028.44957588764, 6362069.8904932579),(560034.94957588764, 6362071.8904932579),(560036.44957588764, 6362071.8904932579),(560037.44957588764, 6362070.3904932579),(560037.44957588764, 6362064.8904932579),(560036.44957588764, 6362063.3904932579),(560034.94957588764, 6362061.3904932579),(560026.94957588764, 6362057.8904932579),(560025.44957588764, 6362057.3904932579),(560023.44957588764, 6362057.3904932579)] gmar = GetMinimumAreaRectangle() # create functor object print "dimensions and area of smallest enclosing rectangular area:" print " {:.3f}(L) x {:.3f}(W) = {:.3f} area".format(*gmar(hull)) # use it输出：
dimensions and area of smallest enclosing rectangular area: 10.393(L) x 18.037(W) = 187.451 area
