(Python)确定(x,y)坐标是否为共线的脚本 - 得到一些错误

Question

就像标题所说的那样,我正在尝试编写一个带有(x,y)坐标列表的程序,并确定是否有3个点共线(位于具有相同斜率的直线上)

我收到一些错误消息.就目前而言,我得到一个"TypeError:'int'对象不可订阅"消息.如果我取出collinearityTest调用areCollinear函数的部分,我会得到一个"索引超出范围"错误.我是python的新手,只是想学习.

def areCollinear(p1, p2, p3):
    slope1 = (p2[1] - p1[1]) / (p2[0] - p1[0])
    slope2 = (p3[1] - p2[1]) / (p3[0] - p2[0])
    if slope1 == slope2:
        print "Points are colinear"
    else:
        print "Points are NOT colinear, what's the matter with you?"

def collinearityTest(pointList):
    position = 0
    while position >=0 and position < len(pointList):

        for p1 in pointList[position]:
            position = position + 1
            for p2 in pointList[position]:
                position = position + 1
                for p3 in pointList[position]:
                    position = position + 1
                    areCollinear(p1, p2, p3)

pointList = [(10, 20), (55, 18), (10, -45.5), (90, 34), (-34, -67), (10, 99)]

collinearityTest(pointList)

错误信息:

Traceback (most recent call last):
  File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 23, in <module>
  File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 19, in collinearityTest
  File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 2, in areCollinear
    if __name__ == '__main__':
TypeError: 'int' object is not subscriptable

Answer 1

这是一个更简单,数值更强大,更稳定的函数来测试三点的共线性:

def collinear(p0, p1, p2):
    x1, y1 = p1[0] - p0[0], p1[1] - p0[1]
    x2, y2 = p2[0] - p0[0], p2[1] - p0[1]
    return abs(x1 * y2 - x2 * y1) < 1e-12

(注意,最好不要对epsilon进行硬编码,并使其相对于向量的长度.)