import cv2

cap = cv2.VideoCapture(0)
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi', fourcc, 20, (640, 480))

while cap.isOpened():
    ret, frame = cap.read()

    if ret == True:
        out.write(frame)
        cv2.imshow('frame', frame)

        if cv2.waitKey(1) == 27:
            break
    else:
        break

cap.release()
out.release()
cv2.destroyAllWindows()