覆盖csv文件，而不是附加在python

Question

Python中的问题-仅将最后一个numpy数组写入.csv文件，而不是将所有数组附加到其后。如何解决此问题？

import cv2, glob
from PIL import Image
import numpy as np
images = glob.glob('*.bmp')
    for image in images:
    img=cv2.imread(image,0)                                #original image
    re=cv2.resize(img, dsize=(128,128), interpolation=cv2.INTER_LINEAR)
    cv2.imwrite("resized_"+image,re)                       #resized image
    a = np.asarray(re)                                     #resized image is converted to pixels
    np.savetxt("sal.csv",a, delimiter=',')
    print(np.asarray(re))                                  #which are printed to csv file. Problem is only the last image pixel values are printed to csv file. Any suggestions to rectify this.