OpenCV throws an error when starting. How to fix?

Question

Python

I have this code

import numpy as np
import cv2
import time

faceCascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

cap = cv2.VideoCapture(1)
cap.set(3,640) 
cap.set(4,480)

while True:
    ret, img = cap.read()
    faces = faceCascade.detectMultiScale(
        scaleFactor = 1.2,
        minNeighbors = 5,
        minSize = (50,50)
    )

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

    cv2.imshow('video',img)

    k = cv2.waitKey(30) & 0xff
    if k == 27: # нажми 'ESC' для выхода
        break

cap.release()
cv2.destroyAllWindows()

It gives me an error:

VIDEOIO ERROR: V4L: can't open camera by index 1
Traceback (most recent call last):
  File "OpenCV.py", line 16, in <module>
    minSize = (50,50)
TypeError: Required argument 'image' (pos 1) not found