import cv2
cap = cv2.VideoCapture(0)
while True:
  ret, frame = cap.read()
  if ret == False: break
  anchoMitad = frame.shape[1] // 2
  frame[:,:anchoMitad] = cv2.flip(frame[:,anchoMitad:],1)
  cv2.imshow('Frame',frame)
  if cv2.waitKey(1) & 0xFF == ord('q'):
    break
cap.release()
cv2.destroyAllWindows()

#Fonte: https://omes-va.com/cv2-flip-en-python-opencv/