CvCapture_MSMF::grabFrame videoio(MSMF): can't grab frame. Error: -2147483638 in python opencv

I have made a face detection program but it's giving me three errors and I tried to solve them through various sites but couldn't find a clear solution

import cv2  
face_cascade = cv2.CascadeClassifier(cv2.data.haarcascades + 'haarcascade_frontalface_default.xml') 
eye_cascade = cv2.CascadeClassifier(cv2.data.haarcascades + 'haarcascade_eye.xml')  
cap = cv2.VideoCapture(0) 
while 1:  

    ret, img = cap.read()  
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
    faces = face_cascade.detectMultiScale(gray, 1.3, 5) 

    for (x,y,w,h) in faces: 
        cv2.rectangle(img,(x,y),(x+w,y+h),(255,255,0),2)  
        roi_gray = gray[y:y+h, x:x+w] 
        roi_color = img[y:y+h, x:x+w] 

        eyes = eye_cascade.detectMultiScale(roi_gray)  

        for (ex,ey,ew,eh) in eyes: 
            cv2.rectangle(roi_color,(ex,ey),(ex+ew,ey+eh),(0,127,255),2) 

    cv2.imshow('img',img) 

    k = cv2.waitKey(30) & 0xff
    if k == 27: 
        break
    
 cap.release()  
 cv2.destroyAllWindows() 

The above code is giving me an error like this

[ WARN:0] global C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-m9hy83n6\opencv\modules\videoio\src\cap_msmf.cpp (912) CvCapture_MSMF::grabFrame videoio(MSMF): can't grab frame. Error: -2147483638
Traceback (most recent call last):
  File "C:\Users\Lenovo\Desktop\code material\Rough.py", line 9, in <module>
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
cv2.error: OpenCV(4.4.0) C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-m9hy83n6\opencv \modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

[ WARN:0] global C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-m9hy83n6\opencv\modules\videoio\src\cap_msmf.cpp (435) `anonymous-namespace'::SourceReaderCB::~SourceReaderCB terminating async callback

please can someone help me with this