how to convert an image to grayscale in python without cv2 code example

Example 1: convert image to grayscale opencv

img = cv2.imread(path)
img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

Example 2: save an image in python as grayscale cv2

cv2.imwrite('data/dst/lena_opencv_red.jpg', im)