OpenCV Python detectMultiscale

大家好，你能给我一些关于OpenCV的建议吗?当我想打印出r以查看rejectLevels时，它只打印出空数组。

#!/usr/bin/python
# -*- coding: utf-8 -*-
import os, sys, logging, time
import numpy as np
import cv2
import cv2.cv as cv

face_cacade = '../home/haarcascade_frontalface_default.xml'
xml = cv2.CascadeClassifier(face_cascade)
array_of_images = [] --> Some images
for image in array_of_images:              
        img   = cv2.imread(image)
        gray  = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
        gray  = cv2.equalizeHist(gray)
        **r**  =  []
        x  =  []
        #cv2.CascadeClassifier.detectMultiScale(image, rejectLevels, levelWeights[, scaleFactor[, minNeighbors[, flags[, minSize[, maxSize[, outputRejectLevels]]]]]]) → objects
        faces = xml.detectMultiScale(image = img, rejectLevels = **r**, levelWeights = x ,scaleFactor=1.05, minNeighbors=1, minSize=(30, 30), flags = cv.CV_HAAR_SCALE_IMAGE)

        file_out  = open('/tmp/faces_score.txt','w+',0)
        for (x,y,w,h) in faces: 
        cv2.rectangle(img,(x,y),(x+w,y+h),(0,255,0),1)
        roi_gray  = gray[y:y+h, x:x+w]
        roi_color = img[y:y+h, x:x+w]
        print **r**, x

你能给我一些解决方案或经验上的Opencv detectMultiScale，我看了c++代码源代码，它看起来很好，但在Python它不会工作，因为它应该是。OpenCV版本:2.4.8Python版本:2.7.6