detectMultiScale函数中的断言失败错误

Question

我正在尝试为opencv中的基本面部识别程序编写代码。这是我第一次尝试，但不断出现此错误，我不知道如何解决。它说 OpenCV（4.0.0）C：\ projects \ opencv-python \ opencv \ modules \ objdetect \ src \ cascadedetect.cpp：1658：错误：（-215：断言失败）函数'cv :: CascadeClassifier中的！empty（）： ：detectMultiScale'

face_c = cv2.CascadeClassifier(r'C:\Users\Srujan Deshpande\Desktop\IO\CV\harrcascade_frontalface_default.xml')
eyes_c = cv2.CascadeClassifier(r'C:\Users\Srujan Deshpande\Desktop\IO\CV\harrcascade_eye.xml')


def detect(gray,frame):
    face = face_c.detectMultiScale(gray,1.3,5)
    for (x,y,w,h) in face:
        cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)
        roi_gray = gray[y:y+h,x:x+w]
        roi_color = frame[y:y+h,x:x+w]
        eyes = eyes_c.detectMultiScale(roi_gray,1.1,25)
        for (ex,ey,ew,eh) in eyes:
            cv2.rectangle(roi_color,(ex,ey),(ex+ew,ey+eh),(0,255,0),2)
    return frame


video_capture = cv2.VideoCapture(0)
while(1):
    _,frame = video_capture.read()
    gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
    canvas = detect(gray,frame)
    cv2.imshow('Video',canvas)
    if cv2.waitKey(1) & 0xFF == ord('q'): break
video_capture.release()
cv2.destroyAllWindows()

我已经放置了.xml文件的整个文件路径，但似乎没有什么区别。