报错信息：cv2.drawContours(thresh_Contours, cnts, -1, (0, 0, 255), 3)
cv2.error: OpenCV(4.5.5) D:\a\opencv-python\opencv-python\opencv\modules\imgproc\src\drawing.cpp:2502: error: (-215:Assertion failed) npoints > 0 in function ‘cv::drawContours’
原因：Opencv版本不同导致报错

cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
                        cv2.CHAIN_APPROX_SIMPLE)[1]
cv2.drawContours(thresh_Contours, cnts, -1, (0, 0, 255), 3)

改正方法：将“1”改成“0”

cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
                        cv2.CHAIN_APPROX_SIMPLE)[0]
cv2.drawContours(thresh_Contours, cnts, -1, (0, 0, 255), 3)